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FGETLN(3)		    Library Functions Manual		     FGETLN(3)

NAME
       fgetln -- get a line from a stream

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<stdio.h>

       char *
       fgetln(FILE *stream, size_t *len);

DESCRIPTION
       The  fgetln()  function	returns	 a  pointer  to	the next line from the
       stream referenced by stream.  This line is not a	C string  as  it  does
       not  end	with a terminating NUL character.  The length of the line, in-
       cluding the final newline, is stored in the memory  location  to	 which
       len  points.   (Note,  however,	that if	the line is the	last in	a file
       that does not end in a newline, the returned text will  not  contain  a
       newline.)

RETURN VALUES
       Upon  successful	completion a pointer is	returned; this pointer becomes
       invalid after the next I/O operation on stream (whether	successful  or
       not)  or	as soon	as the stream is closed.  Otherwise, NULL is returned.
       The fgetln() function does not distinguish between end-of-file and  er-
       ror; the	routines feof(3) and ferror(3) must be used to determine which
       occurred.   If an error occurs, the global variable errno is set	to in-
       dicate the error.  The end-of-file condition is remembered, even	 on  a
       terminal,  and  all  subsequent attempts	to read	will return NULL until
       the condition is	cleared	with clearerr(3).

       The text	to which the returned pointer points may be modified, provided
       that no changes are made	beyond the returned size.  These  changes  are
       lost as soon as the pointer becomes invalid.

ERRORS
       [EBADF]		  The  argument	 stream	is not a stream	open for read-
			  ing.

       [ENOMEM]		  The internal line buffer could not be	 expanded  due
			  to  lack  of	available  memory, or because it would
			  need to expand beyond	INT_MAX	in size.

       The fgetln() function may also fail and set errno for any of the	errors
       specified for the routines fflush(3), malloc(3),	read(2),  stat(2),  or
       realloc(3).

SEE ALSO
       ferror(3), fgets(3), fgetwln(3),	fopen(3), getline(3), putc(3)

HISTORY
       The fgetln() function first appeared in 4.4BSD.

CAVEATS
       Since the returned buffer is not	a C string (it is not NUL terminated),
       a  common practice is to	replace	the newline character with `\0'.  How-
       ever, if	the last line in a file	does not contain a  newline,  the  re-
       turned  text won't contain a newline either.  The following code	demon-
       strates how to deal with	this problem by	allocating a temporary buffer:

	       char *buf, *lbuf;
	       size_t len;

	       lbuf = NULL;
	       while ((buf = fgetln(fp,	&len)) != NULL)	{
		       if (buf[len - 1]	== '\n')
			       buf[len - 1] = '\0';
		       else {
			       /* EOF without EOL, copy	and add	the NUL	*/
			       if ((lbuf = malloc(len +	1)) == NULL)
				       err(1, NULL);
			       memcpy(lbuf, buf, len);
			       lbuf[len] = '\0';
			       buf = lbuf;
		       }
		       printf("%s\n", buf);
	       }
	       free(lbuf);
	       if (ferror(fp))
		       err(1, "fgetln");

FreeBSD	13.2			 June 11, 2020			     FGETLN(3)

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | CAVEATS

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