1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)fgetln.3 8.3 (Berkeley) 4/19/94 29.\" 30.Dd June 11, 2020 31.Dt FGETLN 3 32.Os 33.Sh NAME 34.Nm fgetln 35.Nd get a line from a stream 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In stdio.h 40.Ft char * 41.Fn fgetln "FILE *stream" "size_t *len" 42.Sh DESCRIPTION 43The 44.Fn fgetln 45function 46returns a pointer to the next line from the stream referenced by 47.Fa stream . 48This line is 49.Em not 50a C string as it does not end with a terminating 51.Dv NUL 52character. 53The length of the line, including the final newline, 54is stored in the memory location to which 55.Fa len 56points. 57(Note, however, that if the line is the last 58in a file that 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. 71The 72.Fn fgetln 73function 74does 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 Er 95.It Bq Er EBADF 96The argument 97.Fa stream 98is not a stream open for reading. 99.It Bq Er ENOMEM 100The internal line buffer could not be expanded due to lack of available memory, 101or because it would need to expand beyond INT_MAX in size. 102.El 103.Pp 104The 105.Fn fgetln 106function 107may also fail and set 108.Va errno 109for any of the errors specified for the routines 110.Xr fflush 3 , 111.Xr malloc 3 , 112.Xr read 2 , 113.Xr stat 2 , 114or 115.Xr realloc 3 . 116.Sh SEE ALSO 117.Xr ferror 3 , 118.Xr fgets 3 , 119.Xr fgetwln 3 , 120.Xr fopen 3 , 121.Xr getline 3 , 122.Xr putc 3 123.Sh HISTORY 124The 125.Fn fgetln 126function first appeared in 127.Bx 4.4 . 128.Sh CAVEATS 129Since the returned buffer is not a C string (it is not NUL terminated), a 130common practice is to replace the newline character with 131.Sq \e0 . 132However, if the last line in a file does not contain a newline, 133the returned text won't contain a newline either. 134The following code demonstrates how to deal with this problem by allocating a 135temporary buffer: 136.Bd -literal 137 char *buf, *lbuf; 138 size_t len; 139 140 lbuf = NULL; 141 while ((buf = fgetln(fp, &len)) != NULL) { 142 if (buf[len - 1] == '\en') 143 buf[len - 1] = '\e0'; 144 else { 145 /* EOF without EOL, copy and add the NUL */ 146 if ((lbuf = 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 free(lbuf); 155 if (ferror(fp)) 156 err(1, "fgetln"); 157.Ed 158