Program that checks if two files match. Is this implementation the most appropriate?

Question

I wrote a program that checks if two files (with a different path / name) match or not. The hard and symbolic links between the files are followed to determine it.

I know this is not the best implementation, so I would like some suggestions for improvement, possible problems. What you should change?

code:

#include <unistd.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>

void printUsage()
{
    printf("Use: ./leg <name_file1> <name_file2>.\n");
}

int createStat(const char* file, struct stat* fileStat)
{
    if(stat(file,fileStat) < 0)
    {
        fprintf(stderr,"Error! File %s does not exist.\n",file);
        return 0;
    }
    return 1;
}

int main(int argc, char **argv)
{
    if(argc < 3)
    {    
        printf("Insufficient number of parameters.\n");
        printUsage();
        return -1;
    }

    struct stat fileStat1;
    struct stat fileStat2;
    if(createStat(argv[1],&fileStat1) == 0)
    {
        return -1;
    }
    if(createStat(argv[2],&fileStat2) == 0)
    {
        return -1;
    }
    if(S_ISREG(fileStat1.st_mode) && S_ISREG(fileStat2.st_mode)){
        if((fileStat1.st_dev == fileStat2.st_dev) && (fileStat1.st_ino == fileStat2.st_ino)){
            printf("Files'%s' and '%s' coincide.\n", argv[1], argv[2]);
        }
        else
            printf("Files '%s' and '%s' do not match.\n", argv[1], argv[2]);
    }
    else
        fprintf(stderr,"'%s' and '%s' there are no files.\n",argv[1],argv[2]);

    return 0;
}

Answer 1

if(createStat(argv[1],&fileStat1) == 0)
{
    return -1;
}

It's a good idea to output a diagnostic there:

if(createStat(argv[1], &fileStat1) == 0)
{
    perror(argv[1]);
    return EXIT_FAILURE;
}

---

The S_ISREG test seems at best unnecessary, and at worst harmful - what if the files you want to compare are device files? Or directories? Both of those seem valid uses.

---

Please be consistent with the use of braces. Some conditionals have them only for the if block and not the else. Code is easier to read correctly if you're consistent; I recommend using braces even for single statements.

---

The program would be more useful if it returned 0 only if the pathnames refer to the same file, so that scripts can easily use it (although test -ef already exists for that purpose, so perhaps unnecessary).

---

if(argc < 3)
{    
    printf("Insufficient number of parameters.\n");
    printUsage();
    return -1;
}

We should probably at least warn if too many arguments are supplied, and the error message ought to go to the standard error stream.

if (argc != 3)
{    
    fputs("Incorrect number of arguments.\n", stderr);
    printUsage(stderr);
    return EXIT_FAILURE;
}

---

if(stat(file,fileStat) < 0)
{
    fprintf(stderr,"Error! File %s does not exist.\n",file);

Misleading error message - the file might exist, but have insufficient permissions for us to access. Or any of the other reasons listed in the man page (though mostly they prevent the file existing).