putc

Putc is a standard C library function used to write a single character to a file stream. It is declared in stdio.h and is part of the C standard I/O facilities. The typical prototype is int putc(int ch, FILE *stream).

Behavior and return value: putc converts the given integer ch to unsigned char and writes that character to the specified stream. On success, it returns the character written, promoted to int. If an error occurs or the stream cannot be written to, it returns EOF. The character value should be representable as unsigned char; passing values outside this range yields undefined behavior.

Relation to related functions: putc is intended to have the same effect as fputc. In many implementations, putc may be defined as a macro for efficiency, which can affect how arguments are evaluated (potentially more than once). fputc is the corresponding function that performs the same operation as a function call. putchar is a convenience wrapper that writes to stdout and is equivalent to putc with stdout as the stream.

Usage considerations: Because putc may be implemented as a macro, programmers should be aware of potential multiple evaluations of its arguments in some environments. The return value being EOF on error provides a way to detect failures. In portable code, you can use putc where a specific FILE* stream is targeted, or use putchar when writing to standard output.

See also: fputc, putchar, stdio.h, FILE.