HP 3000 Manuals HP 3000 Manuals
getchar
Reads a character from the standard input stream stdin.
Syntax
include <stdio.h>
int getchar (void);
Parameters
None.
Return Values
x The character read from stdin.
EOF Either an end-of-file was detected or an error occurred.
Description
The getchar function reads one character from the standard input stream
stdin.
The getchar function returns the next character in the currently defined
stdin stream. It returns an EOF on end-of-file or file read error. The
getchar function is identical to getc (stdin).
Examples
The following program reads stdin and echos the contents to stdout. The
program ends when an end of file is encountered on stdin.
#include <stdio.h>
main()
{
int c;
while((c = getchar()) != EOF)
putchar(c);
putchar('\n');
}
The variable c is declared as an int type instead of char because sign
extension, bit shifting, and similar operations can cause unexpected
results with the char type. EOF is defined as a negative number. If EOF
is assigned to a char variable, and chars are not signed in the
implementation, the comparison for EOF will never be true. Therefore,
all examples in this chapter use the int type.
The last putchar() statement in the program outputs a new line, so
further output appears at the beginning of a new line instead of at the
end of the last line of output.
The getchar and putchar functions are most useful in filters (programs
that accept and modify data before passing it on). For example, the
following program puts parentheses around each vowel encountered in the
input:
#include <stdio.h>
main()
{
int c;
while((c = getchar()) != '\n') {
if(vowel(c)) {
putchar('(');
putchar(c);
putchar(')');
}else
putchar(c);
}
}
vowel(c)
char c;
{
switch(c) {
case 'a':
case 'A':
case 'e':
case 'E':
case 'i':
case 'I':
case 'o':
case 'O':
case 'u':
case 'U':
return (1);
default:
return (0);
}
}
The vowel test is placed in the function vowel; the program terminates
when it encounters a new line.
The getc and putc functions can behave exactly like the getchar and
putchar functions by specifying the appropriate file pointer. For
example,
getc(stdin);
is identical to
getchar();
and
putc(c, stdout);
is identical to
putchar(c);
Thus, the putc() call in the previous program can be stated as
putchar(c);
without altering the behavior of the program.
See Also
fread(), getc(), gets(), fscanf(), scanf(), putchar(), ANSI C 4.9.7.6,
POSIX.1 8.1