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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, including the final
     newline, is stored in the memory location to which len points.  (Note, how-
     ever, that if the line is the last in a file that does not end  in  a  new-
     line, the returned text will not contain a newline.)

RETURN VALUES
     Upon  successful completion a pointer is returned; this pointer becomes in-
     valid 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 error; 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 indicate the error.
     The end-of-file condition is remembered, even on a terminal, and all subse-
     quent 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 reading.

     [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 real-
     loc(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'.  However, if
     the last line in a file does not contain a newline, the returned text won't
     contain a newline either.	The following code demonstrates 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 ports 15.quarterly	  June 11, 2020 		       FGETLN(3)

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