xref: /freebsd/lib/libc/stdio/getline.3 (revision 500e59c62d8ca793d3fd3cec7c0d370a404a757d)

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.Dd November 30, 2012
.Dt GETLINE 3
.Os
.Sh NAME
.Nm getdelim ,
.Nm getline
.Nd get a line from a stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd "#define _WITH_GETLINE"
.In stdio.h
.Ft ssize_t
.Fn getdelim "char ** restrict linep" "size_t * restrict linecapp" "int delimiter" " FILE * restrict stream"
.Ft ssize_t
.Fn getline "char ** restrict linep" "size_t * restrict linecapp" " FILE * restrict stream"
.Sh DESCRIPTION
The
.Fn getdelim
function reads a line from
.Fa stream ,
delimited by the character
.Fa delimiter .
The
.Fn getline
function is equivalent to
.Fn getdelim
with the newline character as the delimiter.
The delimiter character is included as part of the line, unless
the end of the file is reached.
.Pp
The caller may provide a pointer to a malloced buffer for the line in
.Fa *linep ,
and the capacity of that buffer in
.Fa *linecapp .
These functions expand the buffer as needed, as if via
.Fn realloc .
If
.Fa linep
points to a
.Dv NULL
pointer, a new buffer will be allocated.
In either case,
.Fa *linep
and
.Fa *linecapp
will be updated accordingly.
.Sh RETURN VALUES
The
.Fn getdelim
and
.Fn getline
functions return the number of characters stored in the buffer, excluding the
terminating
.Dv NUL
character.
The value \-1 is returned if an error occurs, or if end-of-file is reached.
.Sh EXAMPLES
The following code fragment reads lines from a file and
writes them to standard output.
The
.Fn fwrite
function is used in case the line contains embedded
.Dv NUL
characters.
.Bd -literal -offset indent
char *line = NULL;
size_t linecap = 0;
ssize_t linelen;
while ((linelen = getline(&line, &linecap, fp)) > 0)
	fwrite(line, linelen, 1, stdout);
free(line);
.Ed
.Sh COMPATIBILITY
Many application writers used the name
.Va getline
before the
.Fn getline
function was introduced in
.St -p1003.1 ,
so a prototype is not provided by default in order to avoid
compatibility problems.
Applications that wish to use the
.Fn getline
function described herein should either request a strict
.St -p1003.1-2008
environment by defining the macro
.Dv _POSIX_C_SOURCE
to the value 200809 or greater, or by defining the macro
.Dv _WITH_GETLINE ,
prior to the inclusion of
.In stdio.h .
For compatibility with GNU libc, defining either
.Dv _BSD_SOURCE
or
.Dv _GNU_SOURCE
prior to the inclusion of
.In stdio.h
will also make
.Fn getline
available.
.Sh ERRORS
These functions may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Either
.Fa linep
or
.Fa linecapp
is
.Dv NULL .
.It Bq Er EOVERFLOW
No delimiter was found in the first
.Dv SSIZE_MAX
characters.
.El
.Pp
These functions may also fail due to any of the errors specified for
.Fn fgets
and
.Fn malloc .
.Sh SEE ALSO
.Xr fgetln 3 ,
.Xr fgets 3 ,
.Xr malloc 3
.Sh STANDARDS
The
.Fn getdelim
and
.Fn getline
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
These routines first appeared in
.Fx 8.0 .
.Sh BUGS
There are no wide character versions of
.Fn getdelim
or
.Fn getline .