1.\" $NetBSD: csh.1,v 1.14 1997/06/23 20:33:31 pk Exp $ 2.\" 3.\" Copyright (c) 1980, 1990, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)csh.1 8.2 (Berkeley) 1/21/94 35.\" 36.Dd January 21, 1994 37.Dt CSH 1 38.Os BSD 4 39.Sh NAME 40.Nm csh 41.Nd a shell (command interpreter) with C-like syntax 42.Sh SYNOPSIS 43.Nm csh 44.Op Fl bcefinstvVxX 45.Op arg ... 46.Nm csh 47.Op Fl l 48.Sh DESCRIPTION 49The 50.Nm csh 51is a command language interpreter 52incorporating a history mechanism (see 53.Nm History Substitutions ) , 54job control facilities (see 55.Nm Jobs ) , 56interactive file name 57and user name completion (see 58.Nm File Name Completion ) , 59and a C-like syntax. It is used both as an interactive 60login shell and a shell script command processor. 61.Ss Argument list processing 62If the first argument (argument 0) to the shell is 63.Ql Fl \& , 64then this is a login shell. 65A login shell also can be specified by invoking the shell with the 66.Ql Fl l 67flag as the only argument. 68.Pp 69The rest of the flag arguments are interpreted as follows: 70.Bl -tag -width 5n 71.It Fl b 72This flag forces a ``break'' from option processing, causing any further 73shell arguments to be treated as non-option arguments. 74The remaining arguments will not be interpreted as shell options. 75This may be used to pass options to a shell script without confusion 76or possible subterfuge. 77The shell will not run a set-user ID script without this option. 78.It Fl c 79Commands are read from the (single) following argument which must 80be present. 81Any remaining arguments are placed in 82.Ar argv . 83.It Fl e 84The shell exits if any invoked command terminates abnormally 85or yields a non-zero exit status. 86.It Fl f 87The shell will start faster, because it will neither search for nor 88execute commands from the file 89.Pa \&.cshrc 90in the invoker's home directory. 91.It Fl i 92The shell is interactive and prompts for its top-level input, 93even if it appears not to be a terminal. 94Shells are interactive without this option if their inputs 95and outputs are terminals. 96.It Fl l 97The shell is a login shell (only applicable if 98.Fl l 99is the only flag specified). 100.It Fl n 101Commands are parsed, but not executed. 102This aids in syntactic checking of shell scripts. 103.It Fl s 104Command input is taken from the standard input. 105.It Fl t 106A single line of input is read and executed. 107A 108.Ql \e 109may be used to escape the newline at the end of this 110line and continue onto another line. 111.It Fl v 112Causes the 113.Ar verbose 114variable to be set, with the effect 115that command input is echoed after history substitution. 116.It Fl x 117Causes the 118.Ar echo 119variable to be set, so that commands are echoed immediately before execution. 120.It Fl V 121Causes the 122.Ar verbose 123variable to be set even before 124.Pa .cshrc 125is executed. 126.It Fl X 127Is to 128.Fl x 129as 130.Fl V 131is to 132.Fl v . 133.El 134.Pp 135After processing of flag arguments, if arguments remain but none of the 136.Fl c , 137.Fl i , 138.Fl s , 139or 140.Fl t 141options were given, the first argument is taken as the name of a file of 142commands to be executed. 143The shell opens this file, and saves its name for possible resubstitution 144by `$0'. 145Since many systems use either the standard version 6 or version 7 shells 146whose shell scripts are not compatible with this shell, the shell will 147execute such a `standard' shell if the first character of a script 148is not a `#', i.e., if the script does not start with a comment. 149Remaining arguments initialize the variable 150.Ar argv . 151.Pp 152An instance of 153.Nm csh 154begins by executing commands from the file 155.Pa /etc/csh.cshrc 156and, 157if this is a login shell, 158.Pa \&/etc/csh.login . 159It then executes 160commands from 161.Pa \&.cshrc 162in the 163.Ar home 164directory of the invoker, and, if this is a login shell, the file 165.Pa \&.login 166in the same location. 167It is typical for users on crt's to put the command ``stty crt'' 168in their 169.Pa \&.login 170file, and to also invoke 171.Xr tset 1 172there. 173.Pp 174In the normal case, the shell will begin reading commands from the 175terminal, prompting with `% '. 176Processing of arguments and the use of the shell to process files 177containing command scripts will be described later. 178.Pp 179The shell repeatedly performs the following actions: 180a line of command input is read and broken into 181.Ar words . 182This sequence of words is placed on the command history list and parsed. 183Finally each command in the current line is executed. 184.Pp 185When a login shell terminates it executes commands from the files 186.Pa .logout 187in the user's 188.Ar home 189directory and 190.Pa /etc/csh.logout . 191.Ss Lexical structure 192The shell splits input lines into words at blanks and tabs with the 193following exceptions. 194The characters 195`&' `\&|' `;' `<' `>' `(' `)' 196form separate words. 197If doubled in `&&', `\&|\&|', `<<' or `>>' these pairs form single words. 198These parser metacharacters may be made part of other words, or prevented their 199special meaning, by preceding them with `\e'. 200A newline preceded by a `\e' is equivalent to a blank. 201.Pp 202Strings enclosed in matched pairs of quotations, 203`'\|', `\*(ga' or `"', 204form parts of a word; metacharacters in these strings, including blanks 205and tabs, do not form separate words. 206These quotations have semantics to be described later. 207Within pairs of `\'' or `"' characters, a newline preceded by a `\e' gives 208a true newline character. 209.Pp 210When the shell's input is not a terminal, 211the character `#' introduces a comment that continues to the end of the 212input line. 213It is prevented this special meaning when preceded by `\e' 214and in quotations using `\`', `\'', and `"'. 215.Ss Commands 216A simple command is a sequence of words, the first of which 217specifies the command to be executed. 218A simple command or 219a sequence of simple commands separated by `\&|' characters 220forms a pipeline. 221The output of each command in a pipeline is connected to the input of the next. 222Sequences of pipelines may be separated by `;', and are then executed 223sequentially. 224A sequence of pipelines may be executed without immediately 225waiting for it to terminate by following it with an `&'. 226.Pp 227Any of the above may be placed in `(' `)' to form a simple command (that 228may be a component of a pipeline, etc.). 229It is also possible to separate pipelines with `\&|\&|' or `&&' showing, 230as in the C language, 231that the second is to be executed only if the first fails or succeeds 232respectively. (See 233.Em Expressions . ) 234.Ss Jobs 235The shell associates a 236.Ar job 237with each pipeline. It keeps 238a table of current jobs, printed by the 239.Ar jobs 240command, and assigns them small integer numbers. When 241a job is started asynchronously with `&', the shell prints a line that looks 242like: 243.Bd -filled -offset indent 244.Op 1 2451234 246.Ed 247.Pp 248showing that the job which was started asynchronously was job number 2491 and had one (top-level) process, whose process id was 1234. 250.Pp 251If you are running a job and wish to do something else you may hit the key 252.Nm ^Z 253(control-Z) which sends a STOP signal to the current job. 254The shell will then normally show that the job has been `Stopped', 255and print another prompt. You can then manipulate the state of this job, 256putting it in the 257.Em background 258with the 259.Ar bg 260command, or run some other 261commands and eventually bring the job back into the foreground with 262the 263.Em foreground 264command 265.Ar fg . 266A 267.Nm ^Z 268takes effect immediately and 269is like an interrupt in that pending output and unread input are discarded 270when it is typed. There is another special key 271.Nm ^Y 272that does not generate a STOP signal until a program attempts to 273.Xr read 2 274it. 275This request can usefully be typed ahead when you have prepared some commands 276for a job that you wish to stop after it has read them. 277.Pp 278A job being run in the background will stop if it tries to read 279from the terminal. Background jobs are normally allowed to produce output, 280but this can be disabled by giving the command ``stty tostop''. 281If you set this 282tty option, then background jobs will stop when they try to produce 283output like they do when they try to read input. 284.Pp 285There are several ways to refer to jobs in the shell. The character 286`%' introduces a job name. If you wish to refer to job number 1, you can 287name it as `%1'. Just naming a job brings it to the foreground; thus 288`%1' is a synonym for `fg %1', bringing job number 1 back into the foreground. 289Similarly saying `%1 &' resumes job number 1 in the background. 290Jobs can also be named by prefixes of the string typed in to start them, 291if these prefixes are unambiguous, thus `%ex' would normally restart 292a suspended 293.Xr ex 1 294job, if there were only one suspended job whose name began with 295the string `ex'. It is also possible to say `%?string' 296which specifies a job whose text contains 297.Ar string , 298if there is only one such job. 299.Pp 300The shell maintains a notion of the current and previous jobs. 301In output about jobs, the current job is marked with a `+' 302and the previous job with a `\-'. The abbreviation `%+' refers 303to the current job and `%\-' refers to the previous job. For close 304analogy with the syntax of the 305.Ar history 306mechanism (described below), 307`%%' is also a synonym for the current job. 308.Pp 309The job control mechanism requires that the 310.Xr stty 1 311option 312.Ic new 313be set. It is an artifact from a 314.Em new 315implementation 316of the 317tty driver that allows generation of interrupt characters from 318the keyboard to tell jobs to stop. See 319.Xr stty 1 320for details on setting options in the new tty driver. 321.Ss Status reporting 322This shell learns immediately whenever a process changes state. 323It normally informs you whenever a job becomes blocked so that 324no further progress is possible, but only just before it prints 325a prompt. This is done so that it does not otherwise disturb your work. 326If, however, you set the shell variable 327.Ar notify , 328the shell will notify you immediately of changes of status in background 329jobs. 330There is also a shell command 331.Ar notify 332that marks a single process so that its status changes will be immediately 333reported. By default 334.Ar notify 335marks the current process; 336simply say `notify' after starting a background job to mark it. 337.Pp 338When you try to leave the shell while jobs are stopped, you will 339be warned that `You have stopped jobs.' You may use the 340.Ar jobs 341command to see what they are. If you do this or immediately try to 342exit again, the shell will not warn you a second time, and the suspended 343jobs will be terminated. 344.Ss File Name Completion 345When the file name completion feature is enabled by setting 346the shell variable 347.Ar filec 348(see 349.Ic set ) , 350.Nm csh 351will 352interactively complete file names and user names from unique 353prefixes, when they are input from the terminal followed by 354the escape character (the escape key, or control-[) 355For example, 356if the current directory looks like 357.Bd -literal -offset indent 358DSC.OLD bin cmd lib xmpl.c 359DSC.NEW chaosnet cmtest mail xmpl.o 360bench class dev mbox xmpl.out 361.Ed 362.Pp 363and the input is 364.Pp 365.Dl % vi ch<escape> 366.Pp 367.Nm csh 368will complete the prefix ``ch'' 369to the only matching file name ``chaosnet'', changing the input 370line to 371.Pp 372.Dl % vi chaosnet 373.Pp 374However, given 375.Pp 376.Dl % vi D<escape> 377.Pp 378.Nm csh 379will only expand the input to 380.Pp 381.Dl % vi DSC. 382.Pp 383and will sound the terminal bell to indicate that the expansion is 384incomplete, since there are two file names matching the prefix ``D''. 385.Pp 386If a partial file name is followed by the end-of-file character 387(usually control-D), then, instead of completing the name, 388.Nm csh 389will list all file names matching the prefix. For example, 390the input 391.Pp 392.Dl % vi D<control-D> 393.Pp 394causes all files beginning with ``D'' to be listed: 395.Pp 396.Dl DSC.NEW DSC.OLD 397.Pp 398while the input line remains unchanged. 399.Pp 400The same system of escape and end-of-file can also be used to 401expand partial user names, if the word to be completed 402(or listed) begins with the character ``~''. For example, 403typing 404.Pp 405.Dl cd ~ro<escape> 406.Pp 407may produce the expansion 408.Pp 409.Dl cd ~root 410.Pp 411The use of the terminal bell to signal errors or multiple matches 412can be inhibited by setting the variable 413.Ar nobeep . 414.Pp 415Normally, all files in the particular directory are candidates 416for name completion. Files with certain suffixes can be excluded 417from consideration by setting the variable 418.Ar fignore 419to the 420list of suffixes to be ignored. Thus, if 421.Ar fignore 422is set by 423the command 424.Pp 425.Dl % set fignore = (.o .out) 426.Pp 427then typing 428.Pp 429.Dl % vi x<escape> 430.Pp 431would result in the completion to 432.Pp 433.Dl % vi xmpl.c 434.Pp 435ignoring the files "xmpl.o" and "xmpl.out". 436However, if the only completion possible requires not ignoring these 437suffixes, then they are not ignored. In addition, 438.Ar fignore 439does not affect the listing of file names by control-D. All files 440are listed regardless of their suffixes. 441.Ss Substitutions 442We now describe the various transformations the shell performs on the 443input in the order in which they occur. 444.Ss History substitutions 445History substitutions place words from previous command input as portions 446of new commands, making it easy to repeat commands, repeat arguments 447of a previous command in the current command, or fix spelling mistakes 448in the previous command with little typing and a high degree of confidence. 449History substitutions begin with the character `!' and may begin 450.Ar anywhere 451in the input stream (with the proviso that they 452.Nm "do not" 453nest.) 454This `!' may be preceded by a `\e' to prevent its special meaning; for 455convenience, an `!' is passed unchanged when it is followed by a blank, 456tab, newline, `=' or `('. 457(History substitutions also occur when an input line begins with `\*(ua'. 458This special abbreviation will be described later.) 459Any input line that contains history substitution is echoed on the terminal 460before it is executed as it could have been typed without history substitution. 461.Pp 462Commands input from the terminal that consist of one or more words 463are saved on the history list. 464The history substitutions reintroduce sequences of words from these 465saved commands into the input stream. 466The size of the history list is controlled by the 467.Ar history 468variable; the previous command is always retained, 469regardless of the value of the history variable. 470Commands are numbered sequentially from 1. 471.Pp 472For definiteness, consider the following output from the 473.Ar history 474command: 475.Bd -literal -offset indent 476\09 write michael 47710 ex write.c 47811 cat oldwrite.c 47912 diff *write.c 480.Ed 481.Pp 482The commands are shown with their event numbers. 483It is not usually necessary to use event numbers, but the current event 484number can be made part of the 485.Ar prompt 486by placing an `!' in the prompt string. 487.Pp 488With the current event 13 we can refer to previous events by event 489number `!11', relatively as in `!\-2' (referring to the same event), 490by a prefix of a command word 491as in `!d' for event 12 or `!wri' for event 9, or by a string contained in 492a word in the command as in `!?mic?' also referring to event 9. 493These forms, without further change, simply reintroduce the words 494of the specified events, each separated by a single blank. 495As a special case, `!!' refers to the previous command; thus `!!' 496alone is a 497.Ar redo . 498.Pp 499To select words from an event we can follow the event specification by 500a `:' and a designator for the desired words. 501The words of an input line are numbered from 0, 502the first (usually command) word being 0, the second word (first argument) 503being 1, etc. 504The basic word designators are: 505.Pp 506.Bl -tag -width Ds -compact -offset indent 507.It \&0 508first (command) word 509.It Ar n 510.Ar n Ns 'th 511argument 512.It \*(ua 513first argument, i.e., `1' 514.It $ 515last argument 516.It % 517word matched by (immediately preceding) 518.No \&? Ns Ar s Ns \&? 519search 520.It Ar \&x\-y 521range of words 522.It Ar \&\-y 523abbreviates 524.Ar `\&0\-y\' 525.It * 526abbreviates `\*(ua\-$', or nothing if only 1 word in event 527.It Ar x* 528abbreviates 529.Ar `x\-$\' 530.It Ar x\- 531like 532.Ar `x*\' 533but omitting word `$' 534.El 535.Pp 536The `:' separating the event specification from the word designator 537can be omitted if the argument selector begins with a `\*(ua', `$', `*' 538`\-' or `%'. 539After the optional word designator can be 540placed a sequence of modifiers, each preceded by a `:'. 541The following modifiers are defined: 542.Pp 543.Bl -tag -width Ds -compact -offset indent 544.It h 545Remove a trailing pathname component, leaving the head. 546.It r 547Remove a trailing `.xxx' component, leaving the root name. 548.It e 549Remove all but the extension `.xxx' part. 550.It s Ns Ar /l/r/ 551Substitute 552.Ar l 553for 554.Ar r 555.It t 556Remove all leading pathname components, leaving the tail. 557.It \&& 558Repeat the previous substitution. 559.It g 560Apply the change once on each word, prefixing the above, e.g., `g&'. 561.It a 562Apply the change as many times as possible on a single word, prefixing 563the above. It can be used together with `g' to apply a substitution 564globally. 565.It p 566Print the new command line but do not execute it. 567.It q 568Quote the substituted words, preventing further substitutions. 569.It x 570Like q, but break into words at blanks, tabs and newlines. 571.El 572.Pp 573Unless preceded by a `g' the change is applied only to the first 574modifiable word. With substitutions, it is an error for no word to be 575applicable. 576.Pp 577The left hand side of substitutions are not regular expressions in the sense 578of the editors, but instead strings. 579Any character may be used as the delimiter in place of `/'; 580a `\e' quotes the delimiter into the 581.Ar l " " 582and 583.Ar r " " 584strings. 585The character `&' in the right hand side is replaced by the text from 586the left. 587A `\e' also quotes `&'. 588A null 589.Ar l 590(`//') 591uses the previous string either from an 592.Ar l 593or from a 594contextual scan string 595.Ar s 596in 597.No \&`!? Ns Ar s Ns \e?' . 598The trailing delimiter in the substitution may be omitted if a newline 599follows immediately as may the trailing `?' in a contextual scan. 600.Pp 601A history reference may be given without an event specification, e.g., `!$'. 602Here, the reference is to the previous command unless a previous 603history reference occurred on the same line in which case this form repeats 604the previous reference. 605Thus `!?foo?\*(ua !$' gives the first and last arguments 606from the command matching `?foo?'. 607.Pp 608A special abbreviation of a history reference occurs when the first 609non-blank character of an input line is a `\*(ua'. 610This is equivalent to `!:s\*(ua' providing a convenient shorthand for substitutions 611on the text of the previous line. 612Thus `\*(ualb\*(ualib' fixes the spelling of 613`lib' 614in the previous command. 615Finally, a history substitution may be surrounded with `{' and `}' 616if necessary to insulate it from the characters that follow. 617Thus, after `ls \-ld ~paul' we might do `!{l}a' to do `ls \-ld ~paula', 618while `!la' would look for a command starting with `la'. 619.Pp 620.Ss Quotations with \' and \&" 621The quotation of strings by `\'' and `"' can be used 622to prevent all or some of the remaining substitutions. 623Strings enclosed in `\'' are prevented any further interpretation. 624Strings enclosed in `"' may be expanded as described below. 625.Pp 626In both cases the resulting text becomes (all or part of) a single word; 627only in one special case (see 628.Em Command Substitution 629below) does a `"' quoted string yield parts of more than one word; 630`\'' quoted strings never do. 631.Ss Alias substitution 632The shell maintains a list of aliases that can be established, displayed 633and modified by the 634.Ar alias 635and 636.Ar unalias 637commands. 638After a command line is scanned, it is parsed into distinct commands and 639the first word of each command, left-to-right, is checked to see if it 640has an alias. 641If it does, then the text that is the alias for that command is reread 642with the history mechanism available 643as though that command were the previous input line. 644The resulting words replace the 645command and argument list. 646If no reference is made to the history list, then the argument list is 647left unchanged. 648.Pp 649Thus if the alias for `ls' is `ls \-l' the command `ls /usr' would map to 650`ls \-l /usr', the argument list here being undisturbed. 651Similarly if the alias for `lookup' was `grep !\*(ua /etc/passwd' then 652`lookup bill' would map to `grep bill /etc/passwd'. 653.Pp 654If an alias is found, the word transformation of the input text 655is performed and the aliasing process begins again on the reformed input line. 656Looping is prevented if the first word of the new text is the same as the old 657by flagging it to prevent further aliasing. 658Other loops are detected and cause an error. 659.Pp 660Note that the mechanism allows aliases to introduce parser metasyntax. 661Thus, we can `alias print \'pr \e!* \&| lpr\'' to make a command that 662.Ar pr Ns 's 663its arguments to the line printer. 664.Ss Variable substitution 665The shell maintains a set of variables, each of which has as value a list 666of zero or more words. 667Some of these variables are set by the shell or referred to by it. 668For instance, the 669.Ar argv 670variable is an image of the shell's argument list, and words of this 671variable's value are referred to in special ways. 672.Pp 673The values of variables may be displayed and changed by using the 674.Ar set 675and 676.Ar unset 677commands. 678Of the variables referred to by the shell a number are toggles; 679the shell does not care what their value is, 680only whether they are set or not. 681For instance, the 682.Ar verbose 683variable is a toggle that causes command input to be echoed. 684The setting of this variable results from the 685.Fl v 686command line option. 687.Pp 688Other operations treat variables numerically. 689The `@' command permits numeric calculations to be performed and the result 690assigned to a variable. 691Variable values are, however, always represented as (zero or more) strings. 692For the purposes of numeric operations, the null string is considered to be 693zero, and the second and additional words of multiword values are ignored. 694.Pp 695After the input line is aliased and parsed, and before each command 696is executed, variable substitution 697is performed keyed by `$' characters. 698This expansion can be prevented by preceding the `$' with a `\e' except 699within `"'s where it 700.Em always 701occurs, and within `\''s where it 702.Em never 703occurs. 704Strings quoted by `\*(ga' are interpreted later (see 705.Nm "Command substitution" 706below) so `$' substitution does not occur there until later, if at all. 707A `$' is passed unchanged if followed by a blank, tab, or end-of-line. 708.Pp 709Input/output redirections are recognized before variable expansion, 710and are variable expanded separately. 711Otherwise, the command name and entire argument list are expanded together. 712It is thus possible for the first (command) word (to this point) to generate 713more than one word, the first of which becomes the command name, 714and the rest of which become arguments. 715.Pp 716Unless enclosed in `"' or given the `:q' modifier the results of variable 717substitution may eventually be command and filename substituted. 718Within `"', a variable whose value consists of multiple words expands to a 719(portion of) a single word, with the words of the variables value 720separated by blanks. 721When the `:q' modifier is applied to a substitution 722the variable will expand to multiple words with each word separated 723by a blank and quoted to prevent later command or filename substitution. 724.Pp 725The following metasequences are provided for introducing variable values into 726the shell input. 727Except as noted, it is an error to reference a variable that is not set. 728.Pp 729.Bl -tag -width Ds -compact -offset indent 730.It $name 731.It ${name} 732Are replaced by the words of the value of variable 733.Ar name , 734each separated by a blank. 735Braces insulate 736.Ar name 737from following characters that would otherwise be part of it. 738Shell variables have names consisting of up to 20 letters and digits 739starting with a letter. The underscore character is considered a letter. 740If 741.Ar name 742is not a shell variable, but is set in the environment, then 743that value is returned (but 744.Nm : 745modifiers and the other forms 746given below are not available here). 747.It $name Ns Op selector 748.It ${name Ns [ selector ] } 749May be used to select only some of the words from the value of 750.Ar name . 751The selector is subjected to `$' substitution and may consist of a single 752number or two numbers separated by a `\-'. 753The first word of a variables value is numbered `1'. 754If the first number of a range is omitted it defaults to `1'. 755If the last number of a range is omitted it defaults to `$#name'. 756The selector `*' selects all words. 757It is not an error for a range to be empty if the second argument is omitted 758or in range. 759.It $#name 760.It ${#name} 761Gives the number of words in the variable. 762This is useful for later use in a 763`$argv[selector]'. 764.It $0 765Substitutes the name of the file from which command input is being read. 766An error occurs if the name is not known. 767.It $number 768.It ${number} 769Equivalent to 770`$argv[number]'. 771.It $* 772Equivalent to 773`$argv[*]'. 774The modifiers `:e', `:h', `:t', `:r', `:q' and `:x' may be applied to 775the substitutions above as may `:gh', `:gt' and `:gr'. 776If braces `{' '}' appear in the command form then the modifiers 777must appear within the braces. 778The current implementation allows only one `:' modifier on each `$' expansion. 779.El 780.Pp 781The following substitutions may not be modified with `:' modifiers. 782.Bl -tag -width Ds -compact -offset indent 783.It $?name 784.It ${?name} 785Substitutes the string `1' if name is set, `0' if it is not. 786.It $?0 787Substitutes `1' if the current input filename is known, `0' if it is not. 788.It \&$\&$\& 789Substitute the (decimal) process number of the (parent) shell. 790.It $! 791Substitute the (decimal) process number of the last background process 792started by this shell. 793.It $< 794Substitutes a line from the standard 795input, with no further interpretation. 796It can be used to read from the keyboard in a shell script. 797.El 798.Ss Command and filename substitution 799The remaining substitutions, command and filename substitution, 800are applied selectively to the arguments of builtin commands. 801By selectively, we mean that portions of expressions which are 802not evaluated are not subjected to these expansions. 803For commands that are not internal to the shell, the command 804name is substituted separately from the argument list. 805This occurs very late, 806after input-output redirection is performed, and in a child 807of the main shell. 808.Ss Command substitution 809Command substitution is shown by a command enclosed in `\*(ga'. 810The output from such a command is normally broken into separate words 811at blanks, tabs and newlines, with null words being discarded; 812this text then replaces the original string. 813Within `"'s, only newlines force new words; blanks and tabs are preserved. 814.Pp 815In any case, the single final newline does not force a new word. 816Note that it is thus possible for a command substitution to yield 817only part of a word, even if the command outputs a complete line. 818.Ss Filename substitution 819If a word contains any of the characters `*', `?', `[' or `{' 820or begins with the character `~', then that word is a candidate for 821filename substitution, also known as `globbing'. 822This word is then regarded as a pattern, and replaced with an alphabetically 823sorted list of file names that match the pattern. 824In a list of words specifying filename substitution it is an error for 825no pattern to match an existing file name, but it is not required 826for each pattern to match. 827Only the metacharacters `*', `?' and `[' imply pattern matching, 828the characters `~' and `{' being more akin to abbreviations. 829.Pp 830In matching filenames, the character `.' at the beginning of a filename 831or immediately following a `/', as well as the character `/' must 832be matched explicitly. 833The character `*' matches any string of characters, including the null 834string. 835The character `?' matches any single character. 836The sequence 837.Sq Op ... 838matches any one of the characters enclosed. 839Within 840.Sq Op ... , 841a pair of characters separated by `\-' matches any character lexically between 842the two (inclusive). 843.Pp 844The character `~' at the beginning of a filename refers to home 845directories. 846Standing alone, i.e., `~' it expands to the invokers home directory as reflected 847in the value of the variable 848.Ar home . 849When followed by a name consisting of letters, digits and `\-' characters, 850the shell searches for a user with that name and substitutes their 851home directory; thus `~ken' might expand to `/usr/ken' and `~ken/chmach' 852to `/usr/ken/chmach'. 853If the character `~' is followed by a character other than a letter or `/' 854or does not appear at the beginning of a word, 855it is left undisturbed. 856.Pp 857The metanotation `a{b,c,d}e' is a shorthand for `abe ace ade'. 858Left to right order is preserved, with results of matches being sorted 859separately at a low level to preserve this order. 860This construct may be nested. 861Thus, `~source/s1/{oldls,ls}.c' expands to 862`/usr/source/s1/oldls.c /usr/source/s1/ls.c' 863without chance of error 864if the home directory for `source' is `/usr/source'. 865Similarly `../{memo,*box}' might expand to `../memo ../box ../mbox'. 866(Note that `memo' was not sorted with the results of the match to `*box'.) 867As a special case `{', `}' and `{}' are passed undisturbed. 868.Ss Input/output 869The standard input and the standard output of a command may be redirected 870with the following syntax: 871.Pp 872.Bl -tag -width Ds -compact -offset indent 873.It < name 874Open file 875.Ar name 876(which is first variable, command and filename expanded) as the standard 877input. 878.It << word 879Read the shell input up to a line that is identical to 880.Ar word . 881.Ar Word 882is not subjected to variable, filename or command substitution, 883and each input line is compared to 884.Ar word 885before any substitutions are done on the input line. 886Unless a quoting `\e', `"', `\*(aa' or `\*(ga' appears in 887.Ar word , 888variable and command substitution is performed on the intervening lines, 889allowing `\e' to quote `$', `\e' and `\*(ga'. 890Commands that are substituted have all blanks, tabs, and newlines 891preserved, except for the final newline which is dropped. 892The resultant text is placed in an anonymous temporary file that 893is given to the command as its standard input. 894.It > name 895.It >! name 896.It >& name 897.It >&! name 898The file 899.Ar name 900is used as the standard output. 901If the file does not exist then it is created; 902if the file exists, it is truncated; its previous contents are lost. 903.Pp 904If the variable 905.Ar noclobber 906is set, then the file must not exist or be a character special file (e.g., a 907terminal or `/dev/null') or an error results. 908This helps prevent accidental destruction of files. 909Here, the `!' forms can be used to suppress this check. 910.Pp 911The forms involving `&' route the standard error output into the specified 912file as well as the standard output. 913.Ar Name 914is expanded in the same way as `<' input filenames are. 915.It >> name 916.It >>& name 917.It >>! name 918.It >>&! name 919Uses file 920.Ar name 921as the standard output; 922like `>' but places output at the end of the file. 923If the variable 924.Ar noclobber 925is set, then it is an error for the file not to exist unless 926one of the `!' forms is given. 927Otherwise similar to `>'. 928.El 929.Pp 930A command receives the environment in which the shell was 931invoked as modified by the input-output parameters and 932the presence of the command in a pipeline. 933Thus, unlike some previous shells, commands run from a file of shell commands 934have no access to the text of the commands by default; 935instead they receive the original standard input of the shell. 936The `<<' mechanism should be used to present inline data. 937This permits shell command scripts to function as components of pipelines 938and allows the shell to block read its input. 939Note that the default standard input for a command run detached is 940.Ar not 941modified to be the empty file 942.Pa /dev/null ; 943instead the standard input 944remains as the original standard input of the shell. If this is a terminal 945and if the process attempts to read from the terminal, then the process 946will block and the user will be notified (see 947.Sx Jobs 948above). 949.Pp 950The standard error output may be directed through 951a pipe with the standard output. 952Simply use the form `\&|&' instead of just `\&|'. 953.Ss Expressions 954Several of the builtin commands (to be described later) 955take expressions, in which the operators are similar to those of C, with 956the same precedence. 957These expressions appear in the 958.Nm @, 959.Ar exit , 960.Ar if , 961and 962.Ar while 963commands. 964The following operators are available: 965.Bd -ragged -offset indent 966\&|\&| && \&| \*(ua & == != =~ !~ <= >= 967< > << >> + \- * / % ! ~ ( ) 968.Ed 969.Pp 970Here the precedence increases to the right, 971`==' `!=' `=~' and `!~', `<=' `>=' `<' and `>', `<<' and `>>', `+' and `\-', 972`*' `/' and `%' being, in groups, at the same level. 973The `==' `!=' `=~' and `!~' operators compare their arguments as strings; 974all others operate on numbers. 975The operators `=~' and `!~' are like `!=' and `==' except that the right 976hand side is a 977.Ar pattern 978(containing, e.g., `*'s, `?'s and instances of `[...]') 979against which the left hand operand is matched. This reduces the 980need for use of the 981.Ar switch 982statement in shell scripts when all that is really needed is pattern matching. 983.Pp 984Strings that begin with `0' are considered octal numbers. 985Null or missing arguments are considered `0'. 986The result of all expressions are strings, 987which represent decimal numbers. 988It is important to note that no two components of an expression can appear 989in the same word; except when adjacent to components of expressions that 990are syntactically significant to the parser (`&' `\&|' `<' `>' `(' `)'), 991they should be surrounded by spaces. 992.Pp 993Also available in expressions as primitive operands are command executions 994enclosed in `{' and `}' 995and file enquiries of the form 996.Fl l 997.Ar name 998where 999.Ic l 1000is one of: 1001.Bd -literal -offset indent 1002r read access 1003w write access 1004x execute access 1005e existence 1006o ownership 1007z zero size 1008f plain file 1009d directory 1010.Ed 1011.Pp 1012The specified name is command and filename expanded and then tested 1013to see if it has the specified relationship to the real user. 1014If the file does not exist or is inaccessible then all enquiries return 1015false, i.e., `0'. 1016Command executions succeed, returning true, i.e., `1', 1017if the command exits with status 0, otherwise they fail, returning 1018false, i.e., `0'. 1019If more detailed status information is required then the command 1020should be executed outside an expression and the variable 1021.Ar status 1022examined. 1023.Ss Control flow 1024The shell contains several commands that can be used to regulate the 1025flow of control in command files (shell scripts) and 1026(in limited but useful ways) from terminal input. 1027These commands all operate by forcing the shell to reread or skip in its 1028input and, because of the implementation, restrict the placement of some 1029of the commands. 1030.Pp 1031The 1032.Ic foreach , 1033.Ic switch , 1034and 1035.Ic while 1036statements, as well as the 1037.Ic if\-then\-else 1038form of the 1039.Ic if 1040statement require that the major keywords appear in a single simple command 1041on an input line as shown below. 1042.Pp 1043If the shell's input is not seekable, 1044the shell buffers up input whenever a loop is being read 1045and performs seeks in this internal buffer to accomplish the rereading 1046implied by the loop. 1047(To the extent that this allows, backward goto's will succeed on 1048non-seekable inputs.) 1049.Ss Builtin commands 1050Builtin commands are executed within the shell. 1051If a builtin command occurs as any component of a pipeline 1052except the last then it is executed in a subshell. 1053.Pp 1054.Bl -tag -width Ds -compact -offset indent 1055.It Ic alias 1056.It Ic alias Ar name 1057.It Ic alias Ar name wordlist 1058The first form prints all aliases. 1059The second form prints the alias for name. 1060The final form assigns the specified 1061.Ar wordlist 1062as the alias of 1063.Ar name ; 1064.Ar wordlist 1065is command and filename substituted. 1066.Ar Name 1067is not allowed to be 1068.Ar alias 1069or 1070.Ar unalias . 1071.Pp 1072.It Ic alloc 1073Shows the amount of dynamic memory acquired, broken down into used and 1074free memory. 1075With an argument shows the number of free and used blocks in each size 1076category. The categories start at size 8 and double at each step. 1077This command's output may vary across system types, since 1078systems other than the VAX may use a different memory allocator. 1079.Pp 1080.It Ic bg 1081.It Ic bg \&% Ns Ar job ... 1082Puts the current or specified jobs into the background, continuing them 1083if they were stopped. 1084.Pp 1085.It Ic break 1086Causes execution to resume after the 1087.Ic end 1088of the nearest enclosing 1089.Ic foreach 1090or 1091.Ic while . 1092The remaining commands on the current line are executed. 1093Multi-level breaks are thus possible by writing them all on one line. 1094.Pp 1095.It Ic breaksw 1096Causes a break from a 1097.Ic switch , 1098resuming after the 1099.Ic endsw . 1100.Pp 1101.It Ic case Ar label : 1102A label in a 1103.Ic switch 1104statement as discussed below. 1105.Pp 1106.It Ic cd 1107.It Ic cd Ar name 1108.It Ic chdir 1109.It Ic chdir Ar name 1110Change the shell's working directory to directory 1111.Ar name . 1112If no argument is given then change to the home directory of the user. 1113If 1114.Ar name 1115is not found as a subdirectory of the current directory (and does not begin 1116with `/', `./' or `../'), then each 1117component of the variable 1118.Ic cdpath 1119is checked to see if it has a subdirectory 1120.Ar name . 1121Finally, if all else fails but 1122.Ar name 1123is a shell variable whose value begins with `/', then this 1124is tried to see if it is a directory. 1125.Pp 1126.It Ic continue 1127Continue execution of the nearest enclosing 1128.Ic while 1129or 1130.Ic foreach . 1131The rest of the commands on the current line are executed. 1132.Pp 1133.It Ic default : 1134Labels the default case in a 1135.Ic switch 1136statement. 1137The default should come after all 1138.Ic case 1139labels. 1140.Pp 1141.It Ic dirs 1142Prints the directory stack; the top of the stack is at the left, 1143the first directory in the stack being the current directory. 1144.Pp 1145.It Ic echo Ar wordlist 1146.It Ic echo Fl n Ar wordlist 1147The specified words are written to the shell's standard output, separated 1148by spaces, and terminated with a newline unless the 1149.Fl n 1150option is specified. 1151.Pp 1152.It Ic else 1153.It Ic end 1154.It Ic endif 1155.It Ic endsw 1156See the description of the 1157.Ic foreach , 1158.Ic if , 1159.Ic switch , 1160and 1161.Ic while 1162statements below. 1163.Pp 1164.It Ic eval Ar arg ... 1165(As in 1166.Xr sh 1 . ) 1167The arguments are read as input to the shell and the resulting 1168command(s) executed in the context of the current shell. 1169This is usually used to execute commands 1170generated as the result of command or variable substitution, since 1171parsing occurs before these substitutions. See 1172.Xr tset 1 1173for an example of using 1174.Ic eval . 1175.Pp 1176.It Ic exec Ar command 1177The specified command is executed in place of the current shell. 1178.Pp 1179.It Ic exit 1180.It Ic exit Ar (expr ) 1181The shell exits either with the value of the 1182.Ic status 1183variable (first form) or with the value of the specified 1184.Ic expr 1185(second form). 1186.Pp 1187.It Ic fg 1188.It Ic fg % Ns Ar job ... 1189Brings the current or specified jobs into the foreground, continuing them if 1190they were stopped. 1191.Pp 1192.It Ic foreach Ar name (wordlist) 1193.It ... 1194.It Ic end 1195The variable 1196.Ic name 1197is successively set to each member of 1198.Ic wordlist 1199and the sequence of commands between this command and the matching 1200.Ic end 1201are executed. 1202(Both 1203.Ic foreach 1204and 1205.Ic end 1206must appear alone on separate lines.) 1207The builtin command 1208.Ic continue 1209may be used to continue the loop prematurely and the builtin 1210command 1211.Ic break 1212to terminate it prematurely. 1213When this command is read from the terminal, the loop is read once 1214prompting with `?' before any statements in the loop are executed. 1215If you make a mistake typing in a loop at the terminal you can rub it out. 1216.Pp 1217.It Ic glob Ar wordlist 1218Like 1219.Ic echo 1220but no `\e' escapes are recognized and words are delimited 1221by null characters in the output. 1222Useful for programs that wish to use the shell to filename expand a list 1223of words. 1224.Pp 1225.It Ic goto Ar word 1226The specified 1227.Ic word 1228is filename and command expanded to yield a string of the form `label'. 1229The shell rewinds its input as much as possible 1230and searches for a line of the form `label:' 1231possibly preceded by blanks or tabs. 1232Execution continues after the specified line. 1233.Pp 1234.It Ic hashstat 1235Print a statistics line showing how effective the internal hash 1236table has been at locating commands (and avoiding 1237.Ic exec Ns \'s ) . 1238An 1239.Ic exec 1240is attempted for each component of the 1241.Em path 1242where the hash function indicates a possible hit, and in each component 1243that does not begin with a `/'. 1244.Pp 1245.It Ic history 1246.It Ic history Ar n 1247.It Ic history Fl r Ar n 1248.It Ic history Fl h Ar n 1249Displays the history event list; if 1250.Ar n 1251is given only the 1252.Ar n 1253most recent events are printed. 1254The 1255.Fl r 1256option reverses the order of printout to be most recent first 1257instead of oldest first. 1258The 1259.Fl h 1260option causes the history list to be printed without leading numbers. 1261This format produces files suitable for sourcing using the \-h 1262option to 1263.Ic source . 1264.Pp 1265.It Ic if ( Ar expr ) No command 1266If the specified expression evaluates true, then the single 1267.Ar command 1268with arguments is executed. 1269Variable substitution on 1270.Ar command 1271happens early, at the same 1272time it does for the rest of the 1273.Ic if 1274command. 1275.Ar Command 1276must be a simple command, not 1277a pipeline, a command list, or a parenthesized command list. 1278Input/output redirection occurs even if 1279.Ar expr 1280is false, i.e., when command is 1281.Sy not 1282executed (this is a bug). 1283.Pp 1284.It Ic if ( Ar expr ) Ic then 1285.It ... 1286.It Ic else if ( Ar expr2 ) Ic then 1287.It ... 1288.It Ic else 1289.It ... 1290.It Ic endif 1291If the specified 1292.Ar expr 1293is true then the commands up to the first 1294.Ic else 1295are executed; otherwise if 1296.Ar expr2 1297is true then the commands up to the 1298second 1299.Ic else 1300are executed, etc. 1301Any number of 1302.Ic else-if 1303pairs are possible; only one 1304.Ic endif 1305is needed. 1306The 1307.Ic else 1308part is likewise optional. 1309(The words 1310.Ic else 1311and 1312.Ic endif 1313must appear at the beginning of input lines; 1314the 1315.Ic if 1316must appear alone on its input line or after an 1317.Ic else . ) 1318.Pp 1319.It Ic jobs 1320.It Ic jobs Fl l 1321Lists the active jobs; the 1322.Fl l 1323option lists process id's in addition to the normal information. 1324.Pp 1325.It Ic kill % Ns Ar job 1326.It Ic kill Ar pid 1327.It Ic kill Fl sig Ar pid ... 1328.It Ic kill Fl l 1329Sends either the TERM (terminate) signal or the 1330specified signal to the specified jobs or processes. 1331Signals are either given by number or by names (as given in 1332.Pa /usr/include/signal.h, 1333stripped of the prefix ``SIG''). 1334The signal names are listed by ``kill \-l''. 1335There is no default, just saying `kill' does not 1336send a signal to the current job. 1337If the signal being sent is TERM (terminate) or HUP (hangup), 1338then the job or process will be sent a CONT (continue) signal as well. 1339.Pp 1340.It Ic limit 1341.It Ic limit Ar resource 1342.It Ic limit Ar resource maximum-use 1343.It Ic limit Fl h 1344.It Ic limit Fl h Ar resource 1345.It Ic limit Fl h Ar resource maximum-use 1346Limits the consumption by the current process and each process 1347it creates to not individually exceed 1348.Ar maximum-use 1349on the 1350specified 1351.Ar resource . 1352If no 1353.Ar maximum-use 1354is given, then 1355the current limit is printed; if no 1356.Ar resource 1357is given, then 1358all limitations are given. If the 1359.Fl h 1360flag is given, the hard limits are used instead of the current 1361limits. The hard limits impose a ceiling on the values of 1362the current limits. Only the super-user may raise the hard limits, 1363but a user may lower or raise the current limits within the legal range. 1364.Pp 1365Resources controllable currently include 1366.Ar cputime 1367(the maximum 1368number of cpu-seconds to be used by each process), 1369.Ar filesize 1370(the largest single file that can be created), 1371.Ar datasize 1372(the maximum growth of the data+stack region via 1373.Xr sbrk 2 1374beyond the end of the program text), 1375.Ar stacksize 1376(the maximum 1377size of the automatically-extended stack region), and 1378.Ar coredumpsize 1379(the size of the largest core dump that will be created). 1380.Pp 1381The 1382.Ar maximum-use 1383may be given as a (floating point or integer) 1384number followed by a scale factor. For all limits other than 1385.Ar cputime 1386the default scale is `k' or `kilobytes' (1024 bytes); 1387a scale factor of `m' or `megabytes' may also be used. 1388For 1389.Ar cputime 1390the default scale is `seconds'; 1391a scale factor of `m' for minutes 1392or `h' for hours, or a time of the form `mm:ss' giving minutes 1393and seconds also may be used. 1394.Pp 1395For both 1396.Ar resource 1397names and scale factors, unambiguous prefixes 1398of the names suffice. 1399.Pp 1400.It Ic login 1401Terminate a login shell, replacing it with an instance of 1402.Pa /bin/login. 1403This is one way to log off, included for compatibility with 1404.Xr sh 1 . 1405.Pp 1406.It Ic logout 1407Terminate a login shell. 1408Especially useful if 1409.Ic ignoreeof 1410is set. 1411.Pp 1412.It Ic nice 1413.It Ic nice Ar +number 1414.It Ic nice Ar command 1415.It Ic nice Ar +number command 1416The first form sets the 1417scheduling priority 1418for this shell to 4. 1419The second form sets the 1420priority 1421to the given 1422.Ar number . 1423The final two forms run command at priority 4 and 1424.Ar number 1425respectively. 1426The greater the number, the less cpu the process will get. 1427The super-user may specify negative priority by using `nice \-number ...'. 1428.Ar Command 1429is always executed in a sub-shell, and the restrictions 1430placed on commands in simple 1431.Ic if 1432statements apply. 1433.Pp 1434.It Ic nohup 1435.It Ic nohup Ar command 1436The first form can be used in shell scripts to cause hangups to be 1437ignored for the remainder of the script. 1438The second form causes the specified command to be run with hangups 1439ignored. 1440All processes detached with `&' are effectively 1441.Ic nohup Ns \'ed . 1442.Pp 1443.It Ic notify 1444.It Ic notify % Ns Ar job ... 1445Causes the shell to notify the user asynchronously when the status of the 1446current or specified jobs change; normally notification is presented 1447before a prompt. This is automatic if the shell variable 1448.Ic notify 1449is set. 1450.Pp 1451.It Ic onintr 1452.It Ic onintr Fl 1453.It Ic onintr Ar label 1454Control the action of the shell on interrupts. 1455The first form restores the default action of the shell on interrupts 1456which is to terminate shell scripts or to return to the terminal command 1457input level. 1458The second form `onintr \-' causes all interrupts to be ignored. 1459The final form causes the shell to execute a `goto label' when 1460an interrupt is received or a child process terminates because 1461it was interrupted. 1462.Pp 1463In any case, if the shell is running detached and interrupts are 1464being ignored, all forms of 1465.Ic onintr 1466have no meaning and interrupts 1467continue to be ignored by the shell and all invoked commands. 1468Finally 1469.Ic onintr 1470statements are ignored in the system startup files where interrupts 1471are disabled (/etc/csh.cshrc, /etc/csh.login). 1472.Pp 1473.It Ic popd 1474.It Ic popd Ar +n 1475Pops the directory stack, returning to the new top directory. 1476With an argument 1477.Ns \`+ Ar n Ns \' 1478discards the 1479.Ar n Ns \'th 1480entry in the stack. 1481The members of the directory stack are numbered from the top starting at 0. 1482.Pp 1483.It Ic pushd 1484.It Ic pushd Ar name 1485.It Ic pushd Ar n 1486With no arguments, 1487.Ic pushd 1488exchanges the top two elements of the directory stack. 1489Given a 1490.Ar name 1491argument, 1492.Ic pushd 1493changes to the new directory (ala 1494.Ic cd ) 1495and pushes the old current working directory 1496(as in 1497.Ic csw ) 1498onto the directory stack. 1499With a numeric argument, 1500.Ic pushd 1501rotates the 1502.Ar n Ns \'th 1503argument of the directory 1504stack around to be the top element and changes to it. The members 1505of the directory stack are numbered from the top starting at 0. 1506.Pp 1507.It Ic rehash 1508Causes the internal hash table of the contents of the directories in 1509the 1510.Ic path 1511variable to be recomputed. This is needed if new commands are added 1512to directories in the 1513.Ic path 1514while you are logged in. This should only be necessary if you add 1515commands to one of your own directories, or if a systems programmer 1516changes the contents of a system directory. 1517.Pp 1518.It Ic repeat Ar count command 1519The specified 1520.Ar command 1521which is subject to the same restrictions 1522as the 1523.Ar command 1524in the one line 1525.Ic if 1526statement above, 1527is executed 1528.Ar count 1529times. 1530I/O redirections occur exactly once, even if 1531.Ar count 1532is 0. 1533.Pp 1534.It Ic set 1535.It Ic set Ar name 1536.It Ic set Ar name Ns =word 1537.It Ic set Ar name[index] Ns =word 1538.It Ic set Ar name Ns =(wordlist) 1539The first form of the command shows the value of all shell variables. 1540Variables that have other than a single word as their 1541value print as a parenthesized word list. 1542The second form sets 1543.Ar name 1544to the null string. 1545The third form sets 1546.Ar name 1547to the single 1548.Ar word . 1549The fourth form sets 1550the 1551.Ar index Ns 'th 1552component of 1553.Ar name 1554to 1555.Ar word ; 1556this component must already exist. 1557The final form sets 1558.Ar name 1559to the list of words in 1560.Ar wordlist . 1561The value is always command and filename expanded. 1562.Pp 1563These arguments may be repeated to set multiple values in a single set command. 1564Note however, that variable expansion happens for all arguments before any 1565setting occurs. 1566.Pp 1567.It Ic setenv 1568.It Ic setenv Ar name 1569.It Ic setenv Ar name value 1570The first form lists all current environment variables. 1571It is equivalent to 1572.Xr printenv 1 . 1573The last form sets the value of environment variable 1574.Ar name 1575to be 1576.Ar value , 1577a single string. The second form sets 1578.Ar name 1579to an empty string. 1580The most commonly used environment variables 1581.Ev USER , 1582.Ev TERM , 1583and 1584.Ev PATH 1585are automatically imported to and exported from the 1586.Nm csh 1587variables 1588.Ar user , 1589.Ar term , 1590and 1591.Ar path ; 1592there is no need to use 1593.Ic setenv 1594for these. 1595.Pp 1596.It Ic shift 1597.It Ic shift Ar variable 1598The members of 1599.Ic argv 1600are shifted to the left, discarding 1601.Ic argv Ns Bq 1 . 1602It is an error for 1603.Ic argv 1604not to be set or to have less than one word as value. 1605The second form performs the same function on the specified variable. 1606.Pp 1607.It Ic source Ar name 1608.It Ic source Fl h Ar name 1609The shell reads commands from 1610.Ar name . 1611.Ic Source 1612commands may be nested; if they are nested too deeply the shell may 1613run out of file descriptors. 1614An error in a 1615.Ic source 1616at any level terminates all nested 1617.Ic source 1618commands. 1619Normally input during 1620.Ic source 1621commands is not placed on the history list; 1622the \-h option causes the commands to be placed on the 1623history list without being executed. 1624.Pp 1625.It Ic stop 1626.It Ic stop % Ns Ar job ... 1627Stops the current or specified jobs that are executing in the background. 1628.Pp 1629.It Ic suspend 1630Causes the shell to stop in its tracks, much as if it had been sent a stop 1631signal with 1632.Ic ^Z . 1633This is most often used to stop shells started by 1634.Xr su 1 . 1635.Pp 1636.It Ic switch Ar (string) 1637.It Ic case Ar str1 : 1638.It \ \ \ \ \&... 1639.It Ic \ \ \ \ breaksw 1640.It \ \ \ \ \&... 1641.It Ic default : 1642.It \ \ \ \ \&... 1643.It Ic \ \ \ \ breaksw 1644.It Ic endsw 1645Each case label is successively matched against the specified 1646.Ar string 1647which is first command and filename expanded. 1648The file metacharacters `*', `?' and `[...]' 1649may be used in the case labels, 1650which are variable expanded. 1651If none of the labels match before the `default' label is found, then 1652the execution begins after the default label. 1653Each case label and the default label must appear at the beginning of a line. 1654The command 1655.Ic breaksw 1656causes execution to continue after the 1657.Ic endsw . 1658Otherwise control may fall through case labels and the default label as in C. 1659If no label matches and there is no default, execution continues after 1660the 1661.Ic endsw . 1662.Pp 1663.It Ic time 1664.It Ic time Ar command 1665With no argument, a summary of time used by this shell and its children 1666is printed. 1667If arguments are given 1668the specified simple command is timed and a time summary 1669as described under the 1670.Ic time 1671variable is printed. If necessary, an extra shell is created to print the time 1672statistic when the command completes. 1673.Pp 1674.It Ic umask 1675.It Ic umask Ar value 1676The file creation mask is displayed (first form) or set to the specified 1677value (second form). The mask is given in octal. Common values for 1678the mask are 002 giving all access to the group and read and execute 1679access to others or 022 giving all access except write access for 1680users in the group or others. 1681.Pp 1682.It Ic unalias Ar pattern 1683All aliases whose names match the specified pattern are discarded. 1684Thus all aliases are removed by `unalias *'. 1685It is not an error for nothing to be 1686.Ic unaliased . 1687.Pp 1688.It Ic unhash 1689Use of the internal hash table to speed location of executed programs 1690is disabled. 1691.Pp 1692.It Ic unlimit 1693.It Ic unlimit Ar resource 1694.It Ic unlimit Fl h 1695.It Ic unlimit Fl h Ar resource 1696Removes the limitation on 1697.Ar resource . 1698If no 1699.Ar resource 1700is specified, then all 1701.Ar resource 1702limitations are removed. If 1703.Fl h 1704is given, the corresponding hard limits are removed. Only the 1705super-user may do this. 1706.Pp 1707.It Ic unset Ar pattern 1708All variables whose names match the specified pattern are removed. 1709Thus all variables are removed by `unset *'; this has noticeably 1710distasteful side-effects. 1711It is not an error for nothing to be 1712.Ic unset . 1713.Pp 1714.It Ic unsetenv Ar pattern 1715Removes all variables whose name match the specified pattern from the 1716environment. See also the 1717.Ic setenv 1718command above and 1719.Xr printenv 1 . 1720.Pp 1721.It Ic wait 1722Wait for all background jobs. 1723If the shell is interactive, then an interrupt can disrupt the wait. 1724After the interrupt, the shell prints names and job numbers of all jobs 1725known to be outstanding. 1726.It Ic which Ar command 1727Displays the resolved command that will be executed by the shell. 1728.Pp 1729.It Ic while Ar (expr) 1730.It \&... 1731.It Ic end 1732While the specified expression evaluates non-zero, the commands between 1733the 1734.Ic while 1735and the matching 1736.Ic end 1737are evaluated. 1738.Ic Break 1739and 1740.Ic continue 1741may be used to terminate or continue the loop prematurely. 1742(The 1743.Ic while 1744and 1745.Ic end 1746must appear alone on their input lines.) 1747Prompting occurs here the first time through the loop as for the 1748.Ic foreach 1749statement if the input is a terminal. 1750.Pp 1751.It Ic % Ns Ar job 1752Brings the specified job into the foreground. 1753.Pp 1754.It Ic % Ns Ar job Ic & 1755Continues the specified job in the background. 1756.Pp 1757.It Ic @ 1758.It Ic @ Ar name Ns = expr 1759.It Ic @ Ar name[index] Ns = expr 1760The first form prints the values of all the shell variables. 1761The second form sets the specified 1762.Ar name 1763to the value of 1764.Ar expr . 1765If the expression contains `<', `>', `&' or `|' then at least 1766this part of the expression must be placed within `(' `)'. 1767The third form assigns the value of 1768.Ar expr 1769to the 1770.Ar index Ns 'th 1771argument of 1772.Ar name . 1773Both 1774.Ar name 1775and its 1776.Ar index Ns 'th 1777component must already exist. 1778.El 1779.Pp 1780The operators `*=', `+=', etc are available as in C. 1781The space separating the name from the assignment operator is optional. 1782Spaces are, however, mandatory in separating components of 1783.Ar expr 1784which would otherwise be single words. 1785.Pp 1786Special postfix `+\|+' and `\-\|\-' operators increment and decrement 1787.Ar name 1788respectively, i.e., `@ i++'. 1789.Ss Pre-defined and environment variables 1790The following variables have special meaning to the shell. 1791Of these, 1792.Ar argv , 1793.Ar cwd, 1794.Ar home , 1795.Ar path, 1796.Ar prompt , 1797.Ar shell 1798and 1799.Ar status 1800are always set by the shell. 1801Except for 1802.Ar cwd 1803and 1804.Ar status , 1805this setting occurs only at initialization; 1806these variables will not then be modified unless done 1807explicitly by the user. 1808.Pp 1809The shell copies the environment variable 1810.Ev USER 1811into the variable 1812.Ar user , 1813.Ev TERM 1814into 1815.Ar term , 1816and 1817.Ev HOME 1818into 1819.Ar home , 1820and copies these back into the environment whenever the normal 1821shell variables are reset. 1822The environment variable 1823.Ev PATH 1824is likewise handled; it is not 1825necessary to worry about its setting other than in the file 1826.Ar \&.cshrc 1827as inferior 1828.Nm csh 1829processes will import the definition of 1830.Ar path 1831from the environment, and re-export it if you then change it. 1832.Bl -tag -width histchars 1833.It Ic argv 1834Set to the arguments to the shell, it is from this variable that 1835positional parameters are substituted, i.e., `$1' is replaced by 1836`$argv[1]', 1837etc. 1838.It Ic cdpath 1839Gives a list of alternative directories searched to find subdirectories 1840in 1841.Ar chdir 1842commands. 1843.It Ic cwd 1844The full pathname of the current directory. 1845.It Ic echo 1846Set when the 1847.Fl x 1848command line option is given. 1849Causes each command and its arguments 1850to be echoed just before it is executed. 1851For non-builtin commands all expansions occur before echoing. 1852Builtin commands are echoed before command and filename substitution, 1853since these substitutions are then done selectively. 1854.It Ic filec 1855Enable file name completion. 1856.It Ic histchars 1857Can be given a string value to change the characters used in history 1858substitution. The first character of its value is used as the 1859history substitution character, replacing the default character `!'. 1860The second character of its value replaces the character `\(ua' in 1861quick substitutions. 1862.It Ic histfile 1863Can be set to the pathname where history is going to be saved/restored. 1864.It Ic history 1865Can be given a numeric value to control the size of the history list. 1866Any command that has been referenced in this many events will not be 1867discarded. 1868Too large values of 1869.Ar history 1870may run the shell out of memory. 1871The last executed command is always saved on the history list. 1872.It Ic home 1873The home directory of the invoker, initialized from the environment. 1874The filename expansion of 1875.Sq Pa ~ 1876refers to this variable. 1877.It Ic ignoreeof 1878If set the shell ignores 1879end-of-file from input devices which are terminals. 1880This prevents shells from accidentally being killed by control-D's. 1881.It Ic mail 1882The files where the shell checks for mail. 1883This checking is done after each command completion that will 1884result in a prompt, 1885if a specified interval has elapsed. 1886The shell says `You have new mail.' 1887if the file exists with an access time not greater than its modify time. 1888.Pp 1889If the first word of the value of 1890.Ar mail 1891is numeric it specifies a different mail checking interval, in seconds, 1892than the default, which is 10 minutes. 1893.Pp 1894If multiple mail files are specified, then the shell says 1895`New mail in 1896.Ar name Ns ' 1897when there is mail in the file 1898.Ar name . 1899.It Ic noclobber 1900As described in the section on 1901.Sx input/output , 1902restrictions are placed on output redirection to insure that 1903files are not accidentally destroyed, and that `>>' redirections 1904refer to existing files. 1905.It Ic noglob 1906If set, filename expansion is inhibited. 1907This inhibition is most useful in shell scripts that 1908 are not dealing with filenames, 1909or after a list of filenames has been obtained and further expansions 1910are not desirable. 1911.It Ic nonomatch 1912If set, it is not an error for a filename expansion to not match any 1913existing files; instead the primitive pattern is returned. 1914It is still an error for the primitive pattern to be malformed, i.e., 1915`echo [' 1916still gives an error. 1917.It Ic notify 1918If set, the shell notifies asynchronously of job completions; 1919the default is to present job completions just before printing 1920a prompt. 1921.It Ic path 1922Each word of the path variable specifies a directory in which 1923commands are to be sought for execution. 1924A null word specifies the current directory. 1925If there is no 1926.Ar path 1927variable then only full path names will execute. 1928The usual search path is `.', `/bin' and `/usr/bin', but this 1929may vary from system to system. 1930For the super-user the default search path is `/etc', `/bin' and `/usr/bin'. 1931A shell that is given neither the 1932.Fl c 1933nor the 1934.Fl t 1935option will normally hash the contents of the directories in the 1936.Ar path 1937variable after reading 1938.Ar \&.cshrc , 1939and each time the 1940.Ar path 1941variable is reset. If new commands are added to these directories 1942while the shell is active, it may be necessary to do a 1943.Ic rehash 1944or the commands may not be found. 1945.It Ic prompt 1946The string that is printed before each command is read from 1947an interactive terminal input. 1948If a `!' appears in the string it will be replaced by the current event number 1949unless a preceding `\e' is given. 1950Default is `% ', or `# ' for the super-user. 1951.It Ic savehist 1952Is given a numeric value to control the number of entries of the 1953history list that are saved in ~/.history when the user logs out. 1954Any command that has been referenced in this many events will be saved. 1955During start up the shell sources ~/.history into the history list 1956enabling history to be saved across logins. 1957Too large values of 1958.Ar savehist 1959will slow down the shell during start up. 1960If 1961.Ar savehist 1962is just set, the shell will use the value of 1963.Ar history. 1964.It Ic shell 1965The file in which the shell resides. 1966This variable is used in forking shells to interpret files that have execute 1967bits set, but which are not executable by the system. 1968(See the description of 1969.Sx Non-builtin Command Execution 1970below.) 1971Initialized to the (system-dependent) home of the shell. 1972.It Ic status 1973The status returned by the last command. 1974If it terminated abnormally, then 0200 is added to the status. 1975Builtin commands that fail return exit status `1', 1976all other builtin commands set status to `0'. 1977.It Ic time 1978Controls automatic timing of commands. 1979If set, then any command that takes more than this many cpu seconds 1980will cause a line giving user, system, and real times and a utilization 1981percentage which is the ratio of user plus system times to real time 1982to be printed when it terminates. 1983.It Ic verbose 1984Set by the 1985.Fl v 1986command line option, causes the words of each command to be printed 1987after history substitution. 1988.El 1989.Ss Non-builtin command execution 1990When a command to be executed is found to not be a builtin command 1991the shell attempts to execute the command via 1992.Xr execve 2 . 1993Each word in the variable 1994.Ar path 1995names a directory from which the shell will attempt to execute the command. 1996If it is given neither a 1997.Fl c 1998nor a 1999.Fl t 2000option, the shell will hash the names in these directories into an internal 2001table so that it will only try an 2002.Ic exec 2003in a directory if there is a possibility that the command resides there. 2004This shortcut greatly speeds command location when many directories 2005are present in the search path. 2006If this mechanism has been turned off (via 2007.Ic unhash ) , 2008or if the shell was given a 2009.Fl c 2010or 2011.Fl t 2012argument, and in any case for each directory component of 2013.Ar path 2014that does not begin with a `/', 2015the shell concatenates with the given command name to form a path name 2016of a file which it then attempts to execute. 2017.Pp 2018Parenthesized commands are always executed in a subshell. 2019Thus 2020.Pp 2021.Dl (cd ; pwd) ; pwd 2022.Pp 2023prints the 2024.Ar home 2025directory; leaving you where you were (printing this after the home directory), 2026while 2027.Pp 2028.Dl cd ; pwd 2029.Pp 2030leaves you in the 2031.Ar home 2032directory. 2033Parenthesized commands are most often used to prevent 2034.Ic chdir 2035from affecting the current shell. 2036.Pp 2037If the file has execute permissions but is not an 2038executable binary to the system, then it is assumed to be a 2039file containing shell commands and a new shell is spawned to read it. 2040.Pp 2041If there is an 2042.Ic alias 2043for 2044.Ic shell 2045then the words of the alias will be prepended to the argument list to form 2046the shell command. 2047The first word of the 2048.Ic alias 2049should be the full path name of the shell 2050(e.g., `$shell'). 2051Note that this is a special, late occurring, case of 2052.Ic alias 2053substitution, 2054and only allows words to be prepended to the argument list without change. 2055.Ss Signal handling 2056The shell normally ignores 2057.Ar quit 2058signals. 2059Jobs running detached (either by 2060.Ic \&& 2061or the 2062.Ic bg 2063or 2064.Ic %... & 2065commands) are immune to signals generated from the keyboard, including 2066hangups. 2067Other signals have the values which the shell inherited from its parent. 2068The shell's handling of interrupts and terminate signals 2069in shell scripts can be controlled by 2070.Ic onintr . 2071Login shells catch the 2072.Ar terminate 2073signal; otherwise this signal is passed on to children from the state in the 2074shell's parent. 2075Interrupts are not allowed when a login shell is reading the file 2076.Pa \&.logout . 2077.Sh AUTHOR 2078William Joy. 2079Job control and directory stack features first implemented by J.E. Kulp of 2080IIASA, Laxenburg, Austria, 2081with different syntax than that used now. 2082File name completion code written by Ken Greer, HP Labs. 2083Eight-bit implementation Christos S. Zoulas, Cornell University. 2084.Sh FILES 2085.Bl -tag -width /etc/passwd -compact 2086.It Pa ~/.cshrc 2087Read at beginning of execution by each shell. 2088.It Pa ~/.login 2089Read by login shell, after `.cshrc' at login. 2090.It Pa ~/.logout 2091Read by login shell, at logout. 2092.It Pa /bin/sh 2093Standard shell, for shell scripts not starting with a `#'. 2094.It Pa /tmp/sh* 2095Temporary file for `<<'. 2096.It Pa /etc/passwd 2097Source of home directories for `~name'. 2098.El 2099.Sh LIMITATIONS 2100Word lengths \- 2101Words can be no longer than 1024 characters. 2102The system limits argument lists to 10240 characters. 2103The number of arguments to a command that involves filename expansion 2104is limited to 1/6'th the number of characters allowed in an argument list. 2105Command substitutions may substitute no more characters than are 2106allowed in an argument list. 2107To detect looping, the shell restricts the number of 2108.Ic alias 2109substitutions on a single line to 20. 2110.Sh SEE ALSO 2111.Xr sh 1 , 2112.Xr access 2 , 2113.Xr execve 2 , 2114.Xr fork 2 , 2115.Xr pipe 2 , 2116.Xr setrlimit 2 , 2117.Xr sigaction 2 , 2118.Xr umask 2 , 2119.Xr wait 2 , 2120.Xr killpg 3 , 2121.Xr tty 4 , 2122.Xr a.out 5 , 2123.Xr environ 7 , 2124.br 2125.Em An introduction to the C shell 2126.Sh HISTORY 2127.Nm Csh 2128appeared in 2129.Bx 3 . 2130It 2131was a first implementation of a command language interpreter 2132incorporating a history mechanism (see 2133.Sx History Substitutions ) , 2134job control facilities (see 2135.Sx Jobs ) , 2136interactive file name 2137and user name completion (see 2138.Sx File Name Completion ) , 2139and a C-like syntax. 2140There are now many shells that also have these mechanisms, plus 2141a few more (and maybe some bugs too), which are available through the 2142usenet. 2143.Sh BUGS 2144When a command is restarted from a stop, 2145the shell prints the directory it started in if this is different 2146from the current directory; this can be misleading (i.e., wrong) 2147as the job may have changed directories internally. 2148.Pp 2149Shell builtin functions are not stoppable/restartable. 2150Command sequences of the form `a ; b ; c' are also not handled gracefully 2151when stopping is attempted. If you suspend `b', the shell will 2152immediately execute `c'. This is especially noticeable if this 2153expansion results from an 2154.Ar alias . 2155It suffices to place the sequence of commands in ()'s to force it to 2156a subshell, i.e., `( a ; b ; c )'. 2157.Pp 2158Control over tty output after processes are started is primitive; 2159perhaps this will inspire someone to work on a good virtual 2160terminal interface. In a virtual terminal interface much more 2161interesting things could be done with output control. 2162.Pp 2163Alias substitution is most often used to clumsily simulate shell procedures; 2164shell procedures should be provided instead of aliases. 2165.Pp 2166Commands within loops, prompted for by `?', are not placed on the 2167.Ic history 2168list. 2169Control structure should be parsed instead of being recognized as built-in 2170commands. This would allow control commands to be placed anywhere, 2171to be combined with `\&|', and to be used with `&' and `;' metasyntax. 2172.Pp 2173It should be possible to use the `:' modifiers on the output of command 2174substitutions. 2175.Pp 2176The way the 2177.Ic filec 2178facility is implemented is ugly and expensive. 2179