How to use S_ISREG() and S_ISDIR() POSIX Macros? - c

Question

This is a C program I wrote to recursively navigate and output directories and regular files. It compiles and runs fine on my Linux machine. But on Solaris, the dit->d_type == 8 check and the other similar ones don't work because there is no d_type field. An answer I've read to this problem is to use the S_ISREG() and S_ISDIR() macros, but they don't work at all the way I have them in my code currently. I commented out the lines that work on my Linux machine.
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <dirent.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
void helper(DIR *, struct dirent *, struct stat, char *, int, char **);
void dircheck(DIR *, struct dirent *, struct stat, char *, int, char **);
int main(int argc, char *argv[]){
DIR *dip;
struct dirent *dit;
struct stat statbuf;
char currentPath[FILENAME_MAX];
int depth = 0; /*Used to correctly space output*/
/*Open Current Directory*/
if((dip = opendir(".")) == NULL)
return errno;
/*Store Current Working Directory in currentPath*/
if((getcwd(currentPath, FILENAME_MAX)) == NULL)
return errno;
/*Read all items in directory*/
while((dit = readdir(dip)) != NULL){
/*Skips . and ..*/
if(strcmp(dit->d_name, ".") == 0 || strcmp(dit->d_name, "..") == 0)
continue;
if(stat(currentPath, &statbuf) == -1){
perror("stat");
return errno;
}
/*Checks if current item is of the type file (type 8) and no command line arguments
if(dit->d_type == 8 && argv[1] == NULL)*/
if(S_ISREG(statbuf.st_mode) && argv[1] == NULL)
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
/*If a command line argument is given, checks for filename match
if(dit->d_type == 8 && argv[1] != NULL)*/
if(S_ISREG(statbuf.st_mode) && argv[1] != NULL)
if(strcmp(dit->d_name, argv[1]) == 0)
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
/*Checks if current item is of the type directory (type 4)
if(dit->d_type == 4)*/
if(S_ISDIR(statbuf.st_mode))
dircheck(dip, dit, statbuf, currentPath, depth, argv);
}
closedir(dip);
return 0;
}
/*Recursively called helper function*/
void helper(DIR *dip, struct dirent *dit, struct stat statbuf,
char currentPath[FILENAME_MAX], int depth, char *argv[]){
int i = 0;
if((dip = opendir(currentPath)) == NULL)
printf("Error: Failed to open Directory ==> %s\n", currentPath);
while((dit = readdir(dip)) != NULL){
if(strcmp(dit->d_name, ".") == 0 || strcmp(dit->d_name, "..") == 0)
continue;
stat(currentPath, &statbuf);
/*if(dit->d_type == 8 && argv[1] == NULL){*/
if(S_ISREG(statbuf.st_mode) && argv[1] == NULL){
for(i = 0; i < depth; i++)
printf(" ");
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
}
/*if(dit->d_type == 8 && argv[1] != NULL){*/
if(S_ISREG(statbuf.st_mode) && argv[1] != NULL){
if(strcmp(dit->d_name, argv[1]) == 0){
for(i = 0; i < depth; i++)
printf(" ");
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
}
}
/*if(dit->d_type == 4)*/
if(S_ISDIR(statbuf.st_mode))
dircheck(dip, dit, statbuf, currentPath, depth, argv);
}
}
void dircheck(DIR *dip, struct dirent *dit, struct stat statbuf,
char currentPath[FILENAME_MAX], int depth, char *argv[]){
int i = 0;
strcat(currentPath, "/");
strcat(currentPath, dit->d_name);
/*If two directories exist at the same level the path
is built wrong and needs to be corrected*/
if((chdir(currentPath)) == -1){
chdir("..");
getcwd(currentPath, FILENAME_MAX);
strcat(currentPath, "/");
strcat(currentPath, dit->d_name);
for(i = 0; i < depth; i++)
printf (" ");
printf("%s (subdirectory)\n", dit->d_name);
depth++;
helper(dip, dit, statbuf, currentPath, depth, argv);
}
else{
for(i =0; i < depth; i++)
printf(" ");
printf("%s (subdirectory)\n", dit->d_name);
chdir(currentPath);
depth++;
helper(dip, dit, statbuf, currentPath, depth, argv);
}
}

Answer 1

You're using S_ISREG() and S_ISDIR() correctly, you're just using them on the wrong thing.
In your while((dit = readdir(dip)) != NULL) loop in main, you're calling stat on currentPath over and over again without changing currentPath:
if(stat(currentPath, &statbuf) == -1) {
perror("stat");
return errno;
}
Shouldn't you be appending a slash and dit->d_name to currentPath to get the full path to the file that you want to stat? Methinks that similar changes to your other stat calls are also needed.

Answer 2

[Posted on behalf of fossuser] Thanks to "mu is too short" I was able to fix the bug. Here is my working code has been edited in for those looking for a nice example (since I couldn't find any others online).
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <dirent.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
void helper(DIR *, struct dirent *, struct stat, char *, int, char **);
void dircheck(DIR *, struct dirent *, struct stat, char *, int, char **);
int main(int argc, char *argv[]){
DIR *dip;
struct dirent *dit;
struct stat statbuf;
char currentPath[FILENAME_MAX];
int depth = 0; /*Used to correctly space output*/
/*Open Current Directory*/
if((dip = opendir(".")) == NULL)
return errno;
/*Store Current Working Directory in currentPath*/
if((getcwd(currentPath, FILENAME_MAX)) == NULL)
return errno;
/*Read all items in directory*/
while((dit = readdir(dip)) != NULL){
/*Skips . and ..*/
if(strcmp(dit->d_name, ".") == 0 || strcmp(dit->d_name, "..") == 0)
continue;
/*Correctly forms the path for stat and then resets it for rest of algorithm*/
getcwd(currentPath, FILENAME_MAX);
strcat(currentPath, "/");
strcat(currentPath, dit->d_name);
if(stat(currentPath, &statbuf) == -1){
perror("stat");
return errno;
}
getcwd(currentPath, FILENAME_MAX);
/*Checks if current item is of the type file (type 8) and no command line arguments*/
if(S_ISREG(statbuf.st_mode) && argv[1] == NULL)
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
/*If a command line argument is given, checks for filename match*/
if(S_ISREG(statbuf.st_mode) && argv[1] != NULL)
if(strcmp(dit->d_name, argv[1]) == 0)
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
/*Checks if current item is of the type directory (type 4)*/
if(S_ISDIR(statbuf.st_mode))
dircheck(dip, dit, statbuf, currentPath, depth, argv);
}
closedir(dip);
return 0;
}
/*Recursively called helper function*/
void helper(DIR *dip, struct dirent *dit, struct stat statbuf,
char currentPath[FILENAME_MAX], int depth, char *argv[]){
int i = 0;
if((dip = opendir(currentPath)) == NULL)
printf("Error: Failed to open Directory ==> %s\n", currentPath);
while((dit = readdir(dip)) != NULL){
if(strcmp(dit->d_name, ".") == 0 || strcmp(dit->d_name, "..") == 0)
continue;
strcat(currentPath, "/");
strcat(currentPath, dit->d_name);
stat(currentPath, &statbuf);
getcwd(currentPath, FILENAME_MAX);
if(S_ISREG(statbuf.st_mode) && argv[1] == NULL){
for(i = 0; i < depth; i++)
printf(" ");
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
}
if(S_ISREG(statbuf.st_mode) && argv[1] != NULL){
if(strcmp(dit->d_name, argv[1]) == 0){
for(i = 0; i < depth; i++)
printf(" ");
printf("%s (%d bytes)\n", dit->d_name, (int)statbuf.st_size);
}
}
if(S_ISDIR(statbuf.st_mode))
dircheck(dip, dit, statbuf, currentPath, depth, argv);
}
/*Changing back here is necessary because of how stat is done*/
chdir("..");
closedir(dip);
}
void dircheck(DIR *dip, struct dirent *dit, struct stat statbuf,
char currentPath[FILENAME_MAX], int depth, char *argv[]){
int i = 0;
strcat(currentPath, "/");
strcat(currentPath, dit->d_name);
/*If two directories exist at the same level the path
is built wrong and needs to be corrected*/
if((chdir(currentPath)) == -1){
chdir("..");
getcwd(currentPath, FILENAME_MAX);
strcat(currentPath, "/");
strcat(currentPath, dit->d_name);
for(i = 0; i < depth; i++)
printf (" ");
printf("%s (subdirectory)\n", dit->d_name);
depth++;
helper(dip, dit, statbuf, currentPath, depth, argv);
}
else{
for(i =0; i < depth; i++)
printf(" ");
printf("%s (subdirectory)\n", dit->d_name);
chdir(currentPath);
depth++;
helper(dip, dit, statbuf, currentPath, depth, argv);
}
}