Member Avatar for firdousahmad

Help me plz

#include <stdio.h>

int main ( int argc, char *argv[] )
{
    if ( argc != 2 ) 
    {

        printf( "usage: %s filename", argv[0] );
    }
    else 
    {
               FILE *file = fopen( argv[1], "r" );

                if ( file == 0 )
        {
            printf( "Could not open file\n" );
        }
        else 
        {
            int x;
                        while  ( ( x = fgetc( file ) ) != EOF )
            {
                printf( "%c", x );
            }
            fclose( file );
        }
    }
}
  • 4 Contributors
  • 3 Replies
  • 108 Views
  • 8 Hours Discussion Span
  • Latest Post Latest Post by Trentacle

Dani AI

Generated

The code posted by reads a filename from argv and prints its contents; replies from and touched on argument checking and follow-up improvements. Quick clarifications: argc counts the program name, so a program that requires exactly one filename should check for argc == 2; a program that accepts one or more files should test argc < 2 to detect the missing-argument case. Usage and error messages are best sent to stderr and terminated with a nonzero exit code (use EXIT_FAILURE/EXIT_SUCCESS from <stdlib.h>).

For better diagnostics and robustness, check fopen against NULL (not 0) and call perror or print errno when open/read fails. For correctness when printing raw bytes, avoid passing a possibly negative char value directly to character-output functions; cast to unsigned char first or, for best throughput on large files, use block I/O instead of character-by-character loops.

A compact, robust approach is to copy data in chunks with fread/fwrite (this also addresses ’s performance concern):

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

int main(int argc, char *argv[])
{
    FILE *f = fopen(argv[1], "rb");
    if (!f) { perror("open"); return EXIT_FAILURE; }

    char buf[8192];
    size_t n;
    while ((n = fread(buf, 1, sizeof buf, f)) > 0)
        fwrite(buf, 1, n, stdout);

    if (ferror(f)) { perror("read"); fclose(f); return EXIT_FAILURE; }

    fclose(f);
    return EXIT_SUCCESS;
}

Additional practical notes: prefer fprintf(stderr, ...) with a trailing newline for usage text; check ferror after I/O loops; use BUFSIZ or a larger buffer for speed; open with "rb" for binary-safe copies on Windows; and include minimal context (compile command, platform, exact error/warnings) when asking for help, as recommended. For reference see the C library docs for fopen and fread (fopen, fread, ).

Recommended Answers

All 3 Replies

Member Avatar for Lucaci Andrew

Just replace the condition from line 5 with this one: if ( argc < 2 ) and it should work fine.
Tested on Linux: Ubuntu, and on win 7.
On further posts, please post the question as well, because we can't guess that...

Edited by Lucaci Andrew
Member Avatar for deceptikon

"Help me please" is not a good question. Please be specific about what you want help with. I'd also recommend reading this tutorial on how to ask a smart question.

Member Avatar for Trentacle

I'm going to guess you meant to post something more like this:

#include <stdio.h>
int main(int argc, char *argv[])
{
    if (argc != 2) {
        printf("usage: %s filename", argv[0]);
    } else {
        FILE *file = fopen(argv[1], "r");
        if (file == 0) {
            printf("Could not open file\n");
        } else {
            int x;
            while ((x = fgetc(file)) != EOF) {
                printf("%c", x);
            }
            fclose(file);
        }
    }
}

Now, did you have a question? Here are some good questions you might consider asking:

  • "When I run this with the wrong number of arguments, it terminates immediately and the usage message doesn't display! What am I doing wrong?"
  • "This program runs too slowly when I use it on large files. Can you suggest ways to speed it up?"
  • "I tried to use this program in a shell script, but I can't tell from testing $? whether it succeeded or not. How do I make my program return a meaningful value?"
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