UNIX for Dummies Questions & Answers

/* filedata -- display information about a file */

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

/*
* use octarray for determing
* if permission bits set
*/

static short octarray[9] = {0400, 0200, 0100, 0040, 0020, 0010, 0004, 0002, 0001};

/* mnemonic codes for file permissions,
* 10 chars long because of the terminating null
*/

static char perms[10] = "rwxrwxrwx";

int filedata(const char *pathname)
{
struct stat statbuf;
char descrip[10];

int j;

if(stat(pathname, &statbuf) == -1)
{
        fprintf(stderr, "Couldn't stat %s\n", pathname);
        return(-1);
}

/* put permissions into readable form */

for(j = 0; j < 9; j++)
{

 /*
        * test whether permission set
        * using bitwise AND
        */

        if(statbuf.st_mode & octarray[j])
                descrip[j] = perms[j];
        else
	descrip[j] = '-';
}

descrip[9] = '\0'; /* make sure we've got a string */

/* display file information */

printf("\nFile %s :\n", pathname);
printf("Size %ld bytes\n", statbuf.st_size);
printf("User-id %d, Group-id %d\n", statbuf.st_uid,
        statbuf.st_gid);
printf("Permissions: %s\n", descrip);
return(0);
}

$ gcc filedatatest.c -o filedatatest
/usr/lib/gcc/x86_64-redhat-linux/4.4.5/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
$