freebsd-nq/lib/libc/stdio/fgets.3

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.\"     @(#)fgets.3	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt FGETS 3
.Os
.Sh NAME
.Nm fgets ,
.Nm gets
.Nd get a line from a stream
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Ft char *
.Fn fgets "char *str" "int size" "FILE *stream"
.Ft char *
.Fn gets "char *str"
.Sh DESCRIPTION
The
.Fn fgets
function
reads at most one less than the number of characters specified by
.Fa size
from the given
.Fa stream
and stores them in the string
.Fa str .
Reading stops when a newline character is found,
at end-of-file or error.
The newline, if any, is retained.
If any characters are read and there is no error, a
.Ql \e0
character is appended to end the string.
.Pp
The
.Fn gets
function
is equivalent to
.Fn fgets
with an infinite
.Fa size
and a
.Fa stream
of
.Em stdin ,
except that the newline character (if any) is not stored in the string.
It is the caller's responsibility to ensure that the input line,
if any, is sufficiently short to fit in the string.
.Sh RETURN VALUES
.Pp
Upon successful completion,
.Fn fgets
and 
.Fn gets
return
a pointer to the string.
If end-of-file occurs before any characters are read, 
they return
.Dv NULL
and the buffer contents is unchanged.
If an error occurs,
they return
.Dv NULL
and the buffer contents is indeterminate.
The
.Fn fgets
and
.Fn gets
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 ERRORS
.Bl -tag -width [EBADF]
.It Bq Er EBADF
The given
.Fa stream
is not a readable stream.
.El
.Pp
The function
.Fn fgets
may also fail and set
.Va errno
for any of the errors specified for the routines
.Xr fflush 3 ,
.Xr fstat 2 ,
.Xr read 2 ,
or
.Xr malloc 3 .
.Pp
The function
.Fn gets
may also fail and set
.Va errno
for any of the errors specified for the routine
.Xr getchar 3 .
.Sh SEE ALSO
.Xr feof 3 ,
.Xr ferror 3 ,
.Xr fgetln 3
.Sh STANDARDS
The functions
.Fn fgets
and
.Fn gets
conform to
.St -ansiC .
.Sh BUGS
Since it is usually impossible to ensure that the next input line
is less than some arbitrary length, and because overflowing the
input buffer is almost invariably a security violation, programs
should
.Em NEVER
use
.Fn gets .
The
.Fn gets
function
exists purely to conform to
.St -ansiC .