1.\" $OpenBSD: fgetln.3,v 1.8 2000/12/24 00:30:57 aaron Exp $ 2.\" 3.\" Copyright (c) 1990, 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. 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.Dd April 19, 1994 35.Dt FGETLN 3 36.Os 37.Sh NAME 38.Nm fgetln 39.Nd get a line from a stream 40.Sh SYNOPSIS 41.Fd #include <stdio.h> 42.Ft char * 43.Fn fgetln "FILE *stream" "size_t *len" 44.Sh DESCRIPTION 45The 46.Fn fgetln 47function returns a pointer to the next line from the stream referenced by 48.Fa stream . 49This line is 50.Em not 51a C string as it does not end with a terminating 52.Tn NUL 53character. 54The length of the line, including the final newline, 55is stored in the memory location to which 56.Fa len 57points. 58(Note, however, that if the last line in the stream does not end in a newline, 59the returned text will not contain a newline.) 60.Sh RETURN VALUES 61Upon successful completion a pointer is returned; 62this pointer becomes invalid after the next 63.Tn I/O 64operation on 65.Fa stream 66(whether successful or not) 67or as soon as the stream is closed. 68Otherwise, 69.Dv NULL 70is returned. 71.Pp 72The 73.Fn fgetln 74function does not distinguish between end-of-file and error; the routines 75.Xr feof 3 76and 77.Xr ferror 3 78must be used 79to determine which occurred. 80If an error occurs, the global variable 81.Va errno 82is set to indicate the error. 83The end-of-file condition is remembered, even on a terminal, and all 84subsequent attempts to read will return 85.Dv NULL 86until the condition is 87cleared with 88.Xr clearerr 3 . 89.Pp 90The text to which the returned pointer points may be modified, 91provided that no changes are made beyond the returned size. 92These changes are lost as soon as the pointer becomes invalid. 93.Sh ERRORS 94.Bl -tag -width [EBADF] 95.It Bq Er EBADF 96The argument 97.Fa stream 98is not a stream open for reading. 99.El 100.Pp 101The 102.Fn fgetln 103function may also fail and set 104.Va errno 105for any of the errors specified for the routines 106.Xr fflush 3 , 107.Xr malloc 3 , 108.Xr read 2 , 109.Xr stat 2 , 110or 111.Xr realloc 3 . 112.Sh CAVEATS 113Since the returned buffer is not a C string (it is not null terminated), a 114common practice is to replace the newline character with 115.Sq \e0 . 116However, if the last line in a file does not contain a newline, 117the returned text won't contain a newline either. 118The following code demonstrates how to deal with this problem by allocating a 119temporary buffer: 120.Bd -literal 121 char *buf, *lbuf; 122 size_t len; 123 124 lbuf = NULL; 125 while ((buf = fgetln(fp, &len))) { 126 if (buf[len - 1] == '\en') 127 buf[len - 1] = '\e0'; 128 else { 129 if ((lbuf = (char *)malloc(len + 1)) == NULL) 130 err(1, NULL); 131 memcpy(lbuf, buf, len); 132 lbuf[len] = '\e0'; 133 buf = lbuf; 134 } 135 printf("%s\en", buf); 136 137 if (lbuf != NULL) { 138 free(lbuf); 139 lbuf = NULL; 140 } 141 } 142.Ed 143.Sh SEE ALSO 144.Xr ferror 3 , 145.Xr fgets 3 , 146.Xr fopen 3 , 147.Xr fparseln 3 , 148.Xr putc 3 149.Sh HISTORY 150The 151.Fn fgetln 152function first appeared in 153.Bx 4.4 . 154