Rewrote substantial parts of the page, and relicensed under GPL.

[thirdparty/man-pages.git] / man3 / getline.3

.\" Copyright (c) 2001 John Levon <moz@compsoc.man.ac.uk>
.\" Based in part on GNU libc documentation
.\"
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.\" License.
.TH GETLINE 3  2001-10-07 "GNU" "Linux Programmer's Manual"
.SH NAME
getline, getdelim \- delimited string input
.SH SYNOPSIS
.nf
.B #define _GNU_SOURCE
.B #include <stdio.h>
.sp
.BI "ssize_t getline(char **" lineptr ", size_t *" n ", FILE *" stream );
.nl
.BI "ssize_t getdelim(char **" lineptr ", size_t *" n ", int " delim ", FILE *" stream );
.SH DESCRIPTION
.BR getline ()
reads an entire line, storing the address of the buffer containing
the text into
.IR "*lineptr" .
The buffer is null-terminated and includes the newline character, if a
newline delimiter was found.

.\" FIXME: what happens if *lineptr is NULL but *n isn't zero ?
.\" Answer: *n is ignored and a new buffer is allocated
If
.IR "*lineptr"
is NULL, then the
.BR getline ()
routine will allocate a buffer for containing the line, which must be freed
by the user program.
Alternatively, before calling
.BR getline (),
.IR "*lineptr"
can contain a pointer to a
.BR malloc ()\-allocated
buffer
.IR "*n"
bytes in size. If the buffer is not large enough to hold the line read in,
.BR getline ()
resizes the buffer to fit with
.BR realloc (),
updating
.IR "*lineptr"
and
.IR "*n"
as necessary. In either case, on a successful call,
.IR "*lineptr"
and
.IR "*n"
will be updated to reflect the buffer address and size respectively.

.BR getdelim ()
works like
.BR getline (),
except a line delimiter other than newline can be specified as the
.IR delimiter
argument. As with
.BR getline (),
a delimiter character is not added if one was not present
in the input before end of file was reached.

.SH "RETURN VALUE"
On success,
.BR getline ()
and
.BR getdelim ()
return the number of characters read, including the delimiter character,
but not including the terminating null character. This value can be used
to handle embedded null characters in the line read.

Both functions return \-1  on failure to read a line (including end of file
condition).

.SH ERRORS
.TP
.B EINVAL
Bad parameters
.RI ( n
or
.I lineptr
is NULL, or
.I stream
is not valid).

.SH "EXAMPLE"
.nf
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	FILE * fp;
	char * line = NULL;
	size_t len = 0;
	ssize_t read;
	fp = fopen("/etc/motd", "r");
	if (fp == NULL)
		exit(EXIT_FAILURE);
	while ((read = getline(&line, &len, fp)) != \-1) {
		printf("Retrieved line of length %zu :\en", read);
		printf("%s", line);
	}
	if (line)
		free(line);
	return EXIT_SUCCESS;
}
.fi
.SH "CONFORMING TO"
Both 
.BR getline () 
and 
.BR getdelim () 
are GNU extensions.
They are available since libc 4.6.27.

.SH "SEE ALSO"
.BR read (2),
.BR fgets (3),
.BR fopen (3),
.BR fread (3),
.BR gets (3),
.BR scanf (3)