libc/stdio/fgets.3

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.Dd December 6, 2024
.Dt FGETS 3
.Os
.Sh NAME
.Nm fgets ,
.Nm gets_s
.Nd get a line from a stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft char *
.Fn fgets "char * restrict str" "int size" "FILE * restrict stream"
.Fd #define __STDC_WANT_LIB_EXT1__ 1
.Ft char *
.Fn gets_s "char *str" "rsize_t size"
.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_s
function
is equivalent to
.Fn fgets
with a
.Fa stream
of
.Dv stdin ,
except that the newline character (if any) is not stored in the string.
.Pp
The
.Fn gets
function
was unsafe and is no longer available.
.Sh RETURN VALUES
Upon successful completion,
.Fn fgets
and
.Fn gets_s
return
a pointer to the string.
If end-of-file occurs before any characters are read,
they return
.Dv NULL
and the buffer contents remain unchanged.
If an error occurs,
they return
.Dv NULL
and the buffer contents are indeterminate.
The
.Fn fgets
and
.Fn gets_s
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 Er
.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_s
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 ,
.Xr fgetws 3 ,
.Xr getline 3
.Sh STANDARDS
The
.Fn fgets
function conforms to
.St -isoC-99 .
.Fn gets_s
conforms to
.St -isoC-2011
K.3.7.4.1.
.Fn gets
has been removed from
.St -isoC-2011 .
.Sh HISTORY
The functions
.Fn fgets
and
.Fn gets
first appeared in
.At v7 .