ffix

[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  2006-05-17 "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 );

.BI "ssize_t getdelim(char **" lineptr ", size_t *" n ", int " delim \
", FILE *" stream );
.fi
.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.
(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 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 parameters
.RI ( n
or
.I lineptr
is NULL, or
.I stream
is not valid).
.SH "CONFORMING TO"
Both
.BR getline ()
and
.BR getdelim ()
are GNU extensions.
They are available since libc 4.6.27.
.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 "SEE ALSO"
.BR read (2),
.BR fgets (3),
.BR fopen (3),
.BR fread (3),
.BR gets (3),
.BR scanf (3),
.BR feature_test_macros (7)