libc/stdio/getline.3

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.\" $FreeBSD: head/lib/libc/stdio/getline.3 303524 2016-07-30 01:00:16Z bapt $
.\"
.Dd January 16, 2019
.Dt GETLINE 3
.Os
.Sh NAME
.Nm getdelim ,
.Nm getline
.Nd get a line from a stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.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.
.Pp
The functions do not distinguish between end-of-file and error,
and callers must use
.Xr feof 3
and
.Xr ferror 3
to determine which occurred.
.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);
if (ferror(fp))
	perror("getline");
.Ed
.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 ferror 3 ,
.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
.Dx 2.3 .
.Sh BUGS
There are no wide character versions of
.Fn getdelim
or
.Fn getline .