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() or fclose() on the same stream or a call to exit() or abort().

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.

EXAMPLES

Printing to Standard Output

The following example gets the current time, converts it to a string using localtime() and asctime(), 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() 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(); 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

2.5 Standard I/O Streams, fopen, putc, puts

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 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.