NAME
fputs — put a
string on a stream
SYNOPSIS
#include
<stdio.h>
int fputs(const char *restrict s, FILE *restrict stream);
DESCRIPTION
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.
The fputs () function shall write
the null-terminated string pointed to by
s to the stream pointed
to by
stream.
The terminating null byte shall not be written.
[CX] The last data modification and last file
status change timestamps of the file shall be marked for update between the
successful execution of fputs () and the next
successful completion of a call to fflush(3) or
fclose(3) on the same stream or a call to
exit(3) or abort(3).
RETURN VALUE
Upon successful completion, fputs () shall
return a non-negative number. Otherwise, it shall return EOF, set an error
indicator for the stream, [CX] and set
errno to
indicate the error.
ERRORS
Refer to fputc(3).
The following sections are informative.
EXAMPLES
Printing to Standard Output
The following example gets the current time, converts it to a
string using localtime(3) and
asctime(3), and prints it to standard output using
fputs (). It then prints the number of minutes to an
event for which it is waiting.
#include <time.h>
#include <stdio.h>
...
time_t now;
int minutes_to_event;
...
time(&now);
printf("The time is ");
fputs(asctime(localtime(&now)), stdout);
printf("There are still %d minutes to the event.\n",
minutes_to_event);
...
APPLICATION USAGE
The puts(3) function appends a <newline>
while fputs () does not.
This volume of POSIX.1-2024 requires that successful completion simply return a non-negative integer. There are at least three known different implementation conventions for this requirement:
- Return a constant value.
- Return the last character written.
- Return the number of bytes written. Note that this implementation convention cannot be adhered to for strings longer than {INT_MAX} bytes as the value would not be representable in the return type of the function. For backwards-compatibility, implementations can return the number of bytes for strings of up to {INT_MAX} bytes, and return {INT_MAX} for all longer strings.
RATIONALE
The fputs () function is one whose source
code was specified in the referenced The C Programming
Language. In the original edition, the function had no defined return
value, yet many practical implementations would, as a side-effect, return
the value of the last character written as that was the value remaining in
the accumulator used as a return value. In the second edition of the book,
either the fixed value 0 or EOF would be returned depending upon the return
value of ferror(3); however, for compatibility with extant
implementations, several implementations would, upon success, return a
positive value representing the last byte written.
FUTURE DIRECTIONS
None.
SEE ALSO
V2_chap02(3), fopen(3), putc(3), puts(3)
XBD <stdio.h>
CHANGE HISTORY
First released in Issue 1. Derived from Issue 1 of the SVID.
Issue 6
Extensions beyond the ISO C standard are marked.
The fputs () prototype is updated for
alignment with the ISO/IEC 9899:1999
(“ISO C99”) standard.
Issue 7
Changes are made related to support for finegrained timestamps.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0170 [174,412], XSH/TC1-2008/0171 [412], and XSH/TC1-2008/0172 [14] are applied.