putc(3S) — STANDARD I/O FUNCTIONS

NAME

putc, putchar, fputc, putw − put character or word on a stream

SYNOPSIS

#include <stdio.h>

int putc (int c, FILE ∗stream);

int putchar (int c);

int fputc (int c, FILE ∗stream);

int putw (int w, FILE ∗stream);

DESCRIPTION

putc writes c (converted to an unsigned char) onto the output stream [see intro(3)] at the position where the file pointer (if defined) is pointing, and advances the file pointer appropriately. If the file cannot support positioning requests, or stream was opened with append mode, the character is appended to the output stream. putchar(c) is defined as putc(c, stdout). putc and putchar are macros.

fputc behaves like putc, but is a function rather than a macro. fputc runs more slowly than putc, but it takes less space per invocation and its name can be passed as an argument to a function.

putw writes the word (that is, integer) w to the output stream (where the file pointer, if defined, is pointing). The size of a word is the size of an integer and varies from machine to machine. putw neither assumes nor causes special alignment in the file.

DIAGNOSTICS

On success, these functions (with the exception of putw) each return the value they have written. putw returns ferror (stream). On failure, they return the constant EOF. This result will occur, for example, if the file stream is not open for writing or if the output file cannot grow.

NOTES

Because it is implemented as a macro, putc evaluates a stream argument more than once. In particular, putc(c, ∗f++); doesn’t work sensibly. fputc should be used instead.

Because of possible differences in word length and byte ordering, files written using putw are machine-dependent, and may not be read using getw on a different processor.

Functions exist for all the above defined macros. To get the function form, the macro name must be undefined (for example, #undef putc).

— C Development Set

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