Thread: How to tell if a input is file or directory

fstat(2): file status - Linux man page

Found a better link; or at least my eyes thinks the info is easy to read; seems to have the same info on it.
fstat(2) — Arch manual pages

Tim S.

Your "err" routine is pointless.
And you need to check argc before accessing argv[1].
\e is a non-standard escape sequence. Better to use \033 or \x1b.

Code:

#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
 
#define ERRMSG "\033[1;91mError:\033[0m "
#define USAGE  "Usage: thing FILENAME\n"
 
int main(int argc, char **argv)
{
    if (argc != 2)
    {
        printf(ERRMSG USAGE);
        exit(EXIT_FAILURE);
    }
 
    FILE *fin = fopen(argv[1], "r");
    if (!fin)
    {
        printf(ERRMSG "file \"%s\" not found\n", argv[1]);
        exit(EXIT_FAILURE);
    }
 
    struct stat st;
    fstat(fileno(fin), &st);
    if ((st.st_mode & S_IFMT) == S_IFDIR)
    {
        printf(ERRMSG "\"%s\" is a directory\n", argv[1]);
        exit(EXIT_FAILURE);
    }
 
    if ((st.st_mode & S_IFMT) != S_IFREG)
    {
        printf(ERRMSG "\"%s\" is not a regular file\n", argv[1]);
        exit(EXIT_FAILURE);
    }
 
    printf("\"%s\" is a regular file\n", argv[1]);
    fclose(fin);
 
    return 0;
}

Originally Posted by john.c

Your "err" routine is pointless.

I made it a function to avoid redundancy, because I might use the same error message in the future.

Originally Posted by john.c

And you need to check argc before accessing argv[1].

Thanks for telling me, I didn't notice it.

Originally Posted by john.c

\e is a non-standard escape sequence. Better to use \033 or \x1b.

I'll make sure to fix that too. What is the difference between these three escape sequences?
Also, thanks for the example code.

EDIT:
Here is my updated code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>


#define ERRMSG "\033[1;91mError:\033[0m "
#define USAGE "\nUsage: thing [filename]"


int err(unsigned char message, char args[])
{
    if(message == 0)
    {
        printf("%stoo few arguments%s", ERRMSG, USAGE);
    }
    
    if(message == 1)
    {
        printf("%stoo many arguments%s", ERRMSG, USAGE);
    }
    
    if(message == 2)
    {
        printf("%sfile \"%s\" not found", ERRMSG, &args[0]);
    }
    
    if(message == 3)
    {
        printf("%s\"%s\" is a directory", ERRMSG, &args[0]);
    }
    if(message == 4)
    {
        printf("%s\"%s\" is not a normal file", ERRMSG, &args[0]);
    }
    puts("");
    exit(EXIT_FAILURE);
}


int main(int argc, char* argv[])
{
    FILE *fptr;
    
    if(argc < 2)
    {
        err(0, NULL);
    }
    else if(argc > 2)
    {
        err(1, NULL);
    }
    
    fptr = fopen(argv[1], "r");
    
    if(fptr == NULL)
    {
        err(2, argv[1]);
    }
    
    struct stat st;
    fstat(fileno(fptr), &st);
    
    if ((st.st_mode & S_IFMT) == S_IFDIR)
    {
        err(3, argv[1]);
    }
    
    if ((st.st_mode & S_IFMT) != S_IFREG)
    {
        err(4, argv[1]);
    }
    
    fclose(fptr);
    return 0;
}

I am still using the err function for the reasons stated above.