Creating a filesystem in C [closed] - c

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I want to create a ext4 filesystem in C
For example, my C code currently runs
system("mkfs.ext4 /dev/sdc1")
The problem is using system is not recommended and we don't want to have mkfs.ext4 utility in the root file system.
I saw mke2fs.c file in e2fsprog package, Do we need to copy directly the code understanding the implementation or is there any better way of using some library

Answer 1

That command mkfs.ext4 formats a filesystem on a partition, it does not create a partition. If you need to format a filesystem, the best way to do it is to run the mkfs.ext4 tool. It's not a good idea to copy code from e2fsprogs into your own program.
Why don't you want to have the utility there in the filesystem? If you need to use a certain utility, it should be there.
The system call is potentially unsafe because it passes a string to the shell, and it's difficult to safely escape dynamic arguments to avoid the possibility of shell attacks. If you are using a fixed device or a limited set of devices, and not accepting user input for the device, it should be okay to use system.
If you want to avoid using system, you can do something similar with fork and exec. This does not use the shell, so it is safer. But the code is more complex. I included a safer reusable "systemv" function.
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
char *mkfs_ext4_prog = "/sbin/mkfs.ext4";
int systemv(const char *pathname, char *const argv[])
{
int wstatus;
pid_t pid;
pid = fork();
if (pid == -1) {
perror("fork failed");
exit(EXIT_FAILURE);
} else if (pid == 0) {
execv(pathname, argv);
exit(EXIT_FAILURE);
}
if (waitpid(pid, &wstatus, 0) == -1) {
perror("waitpid");
}
if (WIFEXITED(wstatus)) {
return WEXITSTATUS(wstatus);
}
if (WIFSIGNALED(wstatus)) {
fprintf(stderr, "%s killed by signal %d\n", mkfs_ext4_prog, WTERMSIG(wstatus));
}
exit(EXIT_FAILURE);
}
int mkfs_ext4(char *device)
{
char *const argv[] = { mkfs_ext4_prog, "--", device, NULL };
return systemv(mkfs_ext4_prog, argv);
}
int main(void)
{
int status;
char *device;
device = "/dev/sdc1";
status = mkfs_ext4(device);
exit(status);
}