1.\" $NetBSD: fgetln.3,v 1.8 2002/07/10 14:37:15 yamt 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.\" @(#)fgetln.3 8.3 (Berkeley) 4/19/94 35.\" 36.Dd April 19, 1994 37.Dt FGETLN 3 38.Os 39.Sh NAME 40.Nm fgetln 41.Nd get a line from a stream 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]stdio.h\*[Gt] 46.Ft char * 47.Fn fgetln "FILE * restrict stream" "size_t * restrict len" 48.Sh DESCRIPTION 49The 50.Fn fgetln 51function 52returns a pointer to the next line from the stream referenced by 53.Fa stream . 54This line is 55.Em not 56a C string as it does not end with a terminating 57.Dv NUL 58character. 59The length of the line, including the final newline, 60is stored in the memory location to which 61.Fa len 62points. 63(Note, however, that if the line is the last 64in a file that does not end in a newline, 65the returned text will not contain a newline.) 66.Sh RETURN VALUES 67Upon successful completion a pointer is returned; 68this pointer becomes invalid after the next 69.Tn I/O 70operation on 71.Fa stream 72(whether successful or not) 73or as soon as the stream is closed. 74Otherwise, 75.Dv NULL 76is returned. 77The 78.Fn fgetln 79function 80does not distinguish between end-of-file and error; the routines 81.Xr feof 3 82and 83.Xr ferror 3 84must be used 85to determine which occurred. 86If an error occurs, the global variable 87.Va errno 88is set to indicate the error. 89The end-of-file condition is remembered, even on a terminal, and all 90subsequent attempts to read will return 91.Dv NULL 92until the condition is 93cleared with 94.Xr clearerr 3 . 95.Pp 96The text to which the returned pointer points may be modified, 97provided that no changes are made beyond the returned size. 98These changes are lost as soon as the pointer becomes invalid. 99.Sh ERRORS 100.Bl -tag -width [EBADF] 101.It Bq Er EBADF 102The argument 103.Fa stream 104is not a stream open for reading. 105.El 106.Pp 107The 108.Fn fgetln 109function 110may also fail and set 111.Va errno 112for any of the errors specified for the routines 113.Xr fflush 3 , 114.Xr malloc 3 , 115.Xr read 2 , 116.Xr stat 2 , 117or 118.Xr realloc 3 . 119.Sh SEE ALSO 120.Xr ferror 3 , 121.Xr fgets 3 , 122.Xr fopen 3 , 123.Xr putc 3 124.Sh HISTORY 125The 126.Fn fgetln 127function first appeared in 128.Bx 4.4 . 129.Sh CAVEATS 130Since the returned buffer is not a C string (it is not null terminated), a 131common practice is to replace the newline character with 132.Sq \e0 . 133However, if the last line in a file does not contain a newline, 134the returned text won't contain a newline either. 135The following code demonstrates how to deal with this problem by allocating a 136temporary buffer: 137.Bd -literal 138 char *buf, *lbuf; 139 size_t len; 140 141 lbuf = NULL; 142 while ((buf = fgetln(fp, &len))) { 143 if (buf[len - 1] == '\en') 144 buf[len - 1] = '\e0'; 145 else { 146 if ((lbuf = (char *)malloc(len + 1)) == NULL) 147 err(1, NULL); 148 memcpy(lbuf, buf, len); 149 lbuf[len] = '\e0'; 150 buf = lbuf; 151 } 152 printf("%s\en", buf); 153 154 if (lbuf != NULL) { 155 free(lbuf); 156 lbuf = NULL; 157 } 158 } 159.Ed 160