userspace: Implement chown utility

This commit is contained in:
Bananymous 2025-06-28 21:32:59 +03:00
parent ebf2b16d09
commit 5df0e25c1f
3 changed files with 119 additions and 0 deletions

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@ -4,6 +4,7 @@ set(USERSPACE_PROGRAMS
cat
cat-mmap
chmod
chown
cp
dd
dhcp-client

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@ -0,0 +1,9 @@
set(SOURCES
main.cpp
)
add_executable(chown ${SOURCES})
banan_link_library(chown ban)
banan_link_library(chown libc)
install(TARGETS chown OPTIONAL)

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@ -0,0 +1,109 @@
#include <ctype.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
void usage(const char* argv0, int ret)
{
FILE* out = (ret == 0) ? stdout : stderr;
fprintf(out, "usage: %s [OWNER][:[GROUP]] FILE...\n", argv0);
fprintf(out, " Change the owner and/or group of each FILE.\n");
exit(ret);
}
[[noreturn]] void print_error_and_exit(const char* format, ...)
{
va_list args;
va_start(args, format);
vfprintf(stderr, format, args);
va_end(args);
exit(1);
__builtin_unreachable();
}
const passwd* get_user(const char* string)
{
bool is_numeric = true;
for (size_t i = 0; string[i] && is_numeric; i++)
if (!isdigit(string[i]))
is_numeric = false;
if (is_numeric)
return getpwuid(atoll(string));
return getpwnam(string);
}
const group* get_group(const char* string)
{
bool is_numeric = true;
for (size_t i = 0; string[i] && is_numeric; i++)
if (!isdigit(string[i]))
is_numeric = false;
if (is_numeric)
return getgrgid(atoll(string));
return getgrnam(string);
}
int main(int argc, char** argv)
{
if (argc <= 2)
usage(argv[0], 1);
uid_t uid = -1;
gid_t gid = -1;
const char* owner_string = argv[1];
const char* colon = strchr(owner_string, ':');
if (colon == owner_string)
{
const auto* group = get_group(owner_string + 1);
if (group == nullptr)
print_error_and_exit("could not find group %s\n", owner_string + 1);
gid = group->gr_gid;
}
else if (colon == nullptr)
{
const auto* user = get_user(owner_string);
if (user == nullptr)
print_error_and_exit("could not find user %s\n", owner_string);
uid = user->pw_uid;
}
else
{
char* user_name = strndup(owner_string, colon - owner_string);
if (user_name == nullptr)
print_error_and_exit("strndup: %s\n", strerror(errno));
const auto* user = get_user(user_name);
if (user == nullptr)
print_error_and_exit("could not find user %s\n", user_name);
free(user_name);
uid = user->pw_uid;
if (colon[1] == '\0')
gid = user->pw_gid;
else
{
const auto* group = get_group(colon + 1);
if (group == nullptr)
print_error_and_exit("could not find group %s\n", colon + 1);
gid = group->gr_gid;
}
}
int ret = 0;
for (int i = 2; i < argc; i++)
{
if (chown(argv[i], uid, gid) == -1)
{
perror("chown");
ret = 1;
}
}
return ret;
}