1.\" $NetBSD: setmode.3,v 1.24 2024/04/28 22:43:30 rillig Exp $ 2.\" 3.\" Copyright (c) 1989, 1991, 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)setmode.3 8.2 (Berkeley) 4/28/95 31.\" 32.Dd March 12, 2022 33.Dt SETMODE 3 34.Os 35.Sh NAME 36.Nm getmode , 37.Nm setmode 38.Nd modify mode bits 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In unistd.h 43.Ft void * 44.Fn setmode "const char *mode_str" 45.Ft mode_t 46.Fn getmode "const void *set" "mode_t mode" 47.Sh DESCRIPTION 48The 49.Fn setmode 50function accepts a string representation of a file mode change, 51compiles it to binary form, and returns an abstract representation 52that may be passed to 53.Fn getmode . 54The string may be a numeric (octal) or symbolic string of the form 55accepted by 56.Xr chmod 1 , 57and may represent either an exact mode to set or a change to make to 58an existing mode. 59.Pp 60The 61.Fn getmode 62function adjusts the file permission bits given by 63.Fa mode 64according to the compiled change representation 65.Fa set , 66and returns the adjusted mode. 67While only the permission bits are altered, other parts of the file 68mode, particularly the type, may be examined. 69.Pp 70Because some of the possible symbolic values are defined relative to 71the file creation mask, 72.Fn setmode 73may call 74.Xr umask 2 , 75temporarily changing the mask. 76If this occurs, the file creation mask will be restored before 77.Fn setmode 78returns. 79If the calling program changes the value of its file creation mask 80after calling 81.Fn setmode , 82.Fn setmode 83must be called again to recompile the mode string if 84.Fn getmode 85is to modify future file modes correctly. 86.Pp 87If the mode passed to 88.Fn setmode 89is invalid, 90.Fn setmode 91returns 92.Dv NULL . 93.Sh EXAMPLES 94The effects of the shell command 95.Ql "chmod a+x myscript.sh" 96can be duplicated as follows: 97.Bd -literal -offset indent 98const char *file = "myscript.sh"; 99struct stat st; 100mode_t newmode; 101 102stat(file, &st); 103newmode = getmode(setmode("a+x"), st.st_mode); 104chmod(file, newmode); 105.Ed 106.Sh ERRORS 107The 108.Fn setmode 109function 110may fail and set 111.Va errno 112for any of the errors specified for the library routines 113.Xr reallocarr 3 114or 115.Xr strtol 3 . 116In addition, 117.Fn setmode 118may fail and set 119.Va errno 120to: 121.Bl -tag -width Er 122.It Bq Er EINVAL 123The 124.Fa mode 125argument does not represent a valid mode. 126.El 127.Sh SEE ALSO 128.Xr chmod 1 , 129.Xr stat 2 , 130.Xr umask 2 , 131.Xr malloc 3 132.Sh HISTORY 133The 134.Fn getmode 135and 136.Fn setmode 137functions first appeared in 138.Bx 4.4 . 139.Sh BUGS 140Each call to 141.Nm setmode 142allocates a small amount of memory that there is no correct way to 143free. 144.Pp 145The type of 146.Fa set 147should really be some opaque struct type used only by these functions 148rather than 149.Ft void * . 150