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[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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.TH GETLINE 3  2010-06-12 "GNU" "Linux Programmer's Manual"
.SH NAME
getline, getdelim \- delimited string input
.SH SYNOPSIS
.nf
.B #include <stdio.h>
.sp
.BI "ssize_t getline(char **" lineptr ", size_t *" n ", FILE *" stream );

.BI "ssize_t getdelim(char **" lineptr ", size_t *" n ", int " delim \
", FILE *" stream );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR getline (),
.BR getdelim ():
.PD 0
.RS 4
.TP 4
Since glibc 2.10:
_POSIX_C_SOURCE\ >=\ 200809L || _XOPEN_SOURCE\ >=\ 700
.TP
Before glibc 2.10:
_GNU_SOURCE
.RE
.PD
.ad
.SH DESCRIPTION
.BR getline ()
reads an entire line from \fIstream\fP,
storing the address of the buffer containing the text into
.IR "*lineptr" .
The buffer is null-terminated and includes the newline character, if
one was found.

If
.I "*lineptr"
is NULL, then
.BR getline ()
will allocate a buffer for storing the line,
which should be freed by the user program.
(In this case, the value in
.I *n
is ignored.)

Alternatively, before calling
.BR getline (),
.I "*lineptr"
can contain a pointer to a
.BR malloc (3)\-allocated
buffer
.I "*n"
bytes in size.
If the buffer is not large enough to hold the line,
.BR getline ()
resizes it with
.BR realloc (3),
updating
.I "*lineptr"
and
.I "*n"
as necessary.

In either case, on a successful call,
.I "*lineptr"
and
.I "*n"
will be updated to reflect the buffer address and allocated size respectively.

.BR getdelim ()
works like
.BR getline (),
except that a line delimiter other than newline can be specified as the
.I 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 byte.
This value can be used
to handle embedded null bytes 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 arguments
.RI ( n
or
.I lineptr
is NULL, or
.I stream
is not valid).
.SH VERSIONS
These functions are available since libc 4.6.27.
.SH CONFORMING TO
Both
.BR getline ()
and
.BR getdelim ()
were originally GNU extensions.
They were standardized in POSIX.1-2008.
.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);
    }

    free(line);
    exit(EXIT_SUCCESS);
}
.fi
.SH SEE ALSO
.BR read (2),
.BR fgets (3),
.BR fopen (3),
.BR fread (3),
.BR gets (3),
.BR scanf (3)