fgets()

Updated: May 06, 2022

Read a string from a stream

Synopsis:

#include <stdio.h>

char* fgets( char* buf, 
             int n, 
             FILE* fp );

Arguments:

buf
A pointer to a buffer in which fgets() can store the bytes that it reads.
n
The maximum number of bytes to read.
fp
The stream from which to read the string.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The fgets() function reads a string of bytes from the stream specified by fp, and stores them in the array specified by buf.

It stops reading bytes when:

The newline character isn't discarded. A null character is placed immediately after the last byte read into the array.

Note: Don't assume that there's a newline character in every string that you read with fgets(). A newline character isn't present if there are more than n-1 bytes before the newline.

Also, a newline character might not appear as the last character in a file when the end-of-file is reached.

Returns:

Note: Use feof() or ferror() to distinguish an end-of-file condition from an error.

Examples:

 
#include <stdio.h>
#include <stdlib.h>

int main( void )
{
    FILE *fp;
    char buffer[80];
    char *ret;

    fp = fopen( "file", "r" );
    if (fp == NULL) {
        perror ("fopen()");
        return EXIT_FAILURE;
    }

    while (1) {
        ret = fgets( buffer, 80, fp );
        if (ret == NULL) {
            if (feof( fp )) {
                // We're at the end of the file.
                return EXIT_SUCCESS;
            } else {
                // An error occurred.
                perror ("fgets()");
                return EXIT_FAILURE;
            }
        }
        fputs( buffer, stdout );
    }
}

Classification:

ANSI, POSIX 1003.1

Safety:  
Cancellation point Yes
Interrupt handler No
Signal handler No
Thread Yes