UMBC CMSC 201 Fall '05
CSEE | 201 | 201 F'05 | lectures | news | help
NAMEgetc, getchar, fgetc, getw - get character or word from a stream
SYNOPSIS#include <stdio.h> int getc (FILE *stream); int getchar (void); int fgetc (FILE *stream); int getw (FILE *stream);
DESCRIPTIONFgetc and getc return the next character (if it exists) from the named input stream, as an unsigned character converted to an integer. It also moves the file pointer, if defined, ahead one character in stream. getchar is defined as getc(stdin). Each of getc,getchar and fgetc exist as functions in the C library. Getc and getchar are also available as macros in <stdio.h> (see below under CAVEATS for important details on the implementation of these macros.) Getw returns the next word (i.e., integer) from the named input stream. Getw increments the associated file pointer, if defined, to point to the next integer-sized word. Getw assumes no special alignment in the file.
SEE ALSOfclose(3s), ferror(3s), fopen(3s), fread(3s), gets(3s), putc(3s), scanf(3s), stdio(3s), ugetc(3s)
DIAGNOSTICSThese functions return the constant EOF at end-of-file or upon an error. Because EOF is a valid integer, it is not sufficient to detect getw errors. ferror(3S) must be used as well.
WARNINGIf the integer value returned by getc, getchar, or fgetc is stored into a character variable and then compared against the integer constant EOF, the comparison may never succeed, because sign-extension of a character on widening to integer is machine-dependent.
CAVEATSWhen using the macro versions of getc and getchar, the stream argument may be evaluated more than once. Thus, it must not be an expression with side-effects. In particular, getc(*f++) does not work sensibly. In these situations, the macro must either be #undef'd, or fgetc 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.
BUGSWhen using the macros for getc and getchar, hidden external names may be referenced. Although these names are prefixed with an underscore, they may conflict with names which the ANSI C Standard reserves for the user when appearing in a local context. It is thus recommended that users of these macros reserve all names which begin with an underscore for the implementation, and avoid defining such names, even in a local context.