Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 6 ■ Characters
6.9 Read Characters from a File
In our examples so far, we have read characters typed at the keyboard. If we want to read
characters from a file (input.txt, say), we must declare a file pointer (in, say) and associate it
with the file using
FILE * in = fopen("input.txt", "r");
Once this is done, we could read the next character from the file into a char variable (ch, say) with
this statement:
fscanf(in, "%c", &ch);
However, C provides the more convenient function getc (get a character) for reading a character
from a file. It is used as follows:
ch = getc(in);
getc takes one argument, the file pointer (not the name of the file). It reads and returns the next
character in the file. If there are no more characters to read, getc returns EOF. Thus, getc works
exactly like getchar except that getchar reads from the keyboard while getc reads from
a file.
To illustrate, let us write a program that reads one line of data from a file, input.txt, and
prints it on the screen. This is shown as Program P6.9.
Program P6.9
#include <stdio.h>
int main() {
char ch;
FILE *in = fopen("input.txt", "r");
while ((ch = getc(in)) != '\n')
putchar(ch);
putchar('\n');
fclose(in);
}
This program uses the standard function putchar to write a single character to the standard
output. (Like getchar, putchar is a macro but the distinction is not important for our purposes.)
It takes a character value as its only argument and writes the character in the next position in
the output. However, if the character is a control character, the effect of the character is produced.
For example,
putchar('\n');
will end the current output line – the same effect as if “Enter” or “Return” is pressed.
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