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.\"     @(#)fgetline.3	5.4 (Berkeley) 4/19/91
.\"
.Dd April 19, 1991
.Dt FGETLINE 3
.Os
.Sh NAME
.Nm fgetline
.Nd get a line from a stream
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Ft char *
.Fn fgetline "FILE *stream" "size_t *len"
.Sh DESCRIPTION
The
.Fn fgetline
function
returns a pointer to the next line from the stream referenced by
.Fa stream .
The newline character at the end of the line is replaced by a
.Dv NUL .
.Pp
If
.Fa len
is non-NULL, the length of the line, not counting the terminating
.Dv NUL ,
is stored in the memory location it references.
.Sh RETURN VALUES
Upon successful completion a pointer is returned;
this pointer becomes invalid after the next
.Tn I/O
operation on
.Fa stream
(whether successful or not)
or as soon as the stream is closed.
Otherwise,
.Dv NULL
is returned.
The
.Fn fgetline
function
does not distinguish between end-of-file and error; the routines
.Xr feof 3
and
.Xr ferror 3
must be used
to determine which occurred.
If an error occurrs, the global variable
.Va errno
is set to indicate the error.
The end-of-file condition is remembered, even on a terminal, and all
subsequent attempts to read will return
.Dv NULL
until the condition is
cleared with
.Xr clearerr 3 .
.Pp
The text to which the returned pointer points may be modified,
provided that no changes are made beyond the terminating
.Dv NUL .
These changes are lost as soon as the pointer becomes invalid.
.Sh ERRORS
.Bl -tag -width [EBADF]
.It Bq Er EBADF
The argument
.Fa stream
is not a stream open for reading.
.El
.Pp
The
.Fn fgetline
function
may also fail and set
.Va errno
for any of the errors specified for the routines
.Xr fflush 3 ,
.Xr malloc 3 ,
.Xr read 2 ,
.Xr stat 2 ,
or
.Xr realloc 3 .
.Sh SEE ALSO
.Xr ferror 3 ,
.Xr fgets 3 ,
.Xr fopen 3 ,
.Xr putc 3
.Sh HISTORY
The
.Fn fgetline
function is
.Ud .
.Sh BUGS
It is not possible to tell whether the final line of an input file
was terminated with a newline.