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FreeBSD 11.0 - man page for getline (freebsd section 3)

GETLINE(3)						   BSD Library Functions Manual 						GETLINE(3)

NAME
getdelim, getline -- get a line from a stream
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#define _WITH_GETLINE #include <stdio.h> ssize_t getdelim(char ** restrict linep, size_t * restrict linecapp, int delimiter, FILE * restrict stream); ssize_t getline(char ** restrict linep, size_t * restrict linecapp, FILE * restrict stream);
DESCRIPTION
The getdelim() function reads a line from stream, delimited by the character delimiter. The getline() function is equivalent to 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. The caller may provide a pointer to a malloced buffer for the line in *linep, and the capacity of that buffer in *linecapp. These functions expand the buffer as needed, as if via realloc(). If linep points to a NULL pointer, a new buffer will be allocated. In either case, *linep and *linecapp will be updated accordingly.
RETURN VALUES
The getdelim() and getline() functions return the number of characters stored in the buffer, excluding the terminating NUL character. The value -1 is returned if an error occurs, or if end-of-file is reached.
EXAMPLES
The following code fragment reads lines from a file and writes them to standard output. The fwrite() function is used in case the line con- tains embedded NUL characters. char *line = NULL; size_t linecap = 0; ssize_t linelen; while ((linelen = getline(&line, &linecap, fp)) > 0) fwrite(line, linelen, 1, stdout); free(line);
COMPATIBILITY
Many application writers used the name getline before the getline() function was introduced in IEEE Std 1003.1 (``POSIX.1''), so a prototype is not provided by default in order to avoid compatibility problems. Applications that wish to use the getline() function described herein should either request a strict IEEE Std 1003.1-2008 (``POSIX.1'') environment by defining the macro _POSIX_C_SOURCE to the value 200809 or greater, or by defining the macro _WITH_GETLINE, prior to the inclusion of <stdio.h>. For compatibility with GNU libc, defining either _BSD_SOURCE or _GNU_SOURCE prior to the inclusion of <stdio.h> will also make getline() available.
ERRORS
These functions may fail if: [EINVAL] Either linep or linecapp is NULL. [EOVERFLOW] No delimiter was found in the first SSIZE_MAX characters. These functions may also fail due to any of the errors specified for fgets() and malloc().
SEE ALSO
fgetln(3), fgets(3), malloc(3)
STANDARDS
The getdelim() and getline() functions conform to IEEE Std 1003.1-2008 (``POSIX.1'').
HISTORY
These routines first appeared in FreeBSD 8.0.
BUGS
There are no wide character versions of getdelim() or getline().
BSD
November 30, 2012 BSD