1 files changed, 63 insertions, 0 deletions
diff --git a/command/groups.c b/command/groups.c
new file mode 100644
index 0000000..cb950be
--- /dev/null
+++ b/command/groups.c
@@ -0,0 +1,63 @@
+#include "args.h"
+#include "command.h"
+#include "lslib.h"
+
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static void help (void) {
+    printf("Usage: groups [USER]\n\n");
+    printf("Print the groups USER is in\n");
+}
+
+COMMAND(groups) {
+
+    uid_t uid;
+    int ngroups, i;
+    gid_t* groups;
+    struct passwd* pw;
+
+    parse_help(argc, argv, help);
+    
+    if (argc < 1) {
+        uid = getuid();
+        pw = getpwuid(uid);
+    } else {
+        pw = getpwnam(argv[0]);
+    }
+
+    if(pw == NULL){
+        if (errno == 0) {
+            error("user not found");
+        } else {
+            error("failed to fetch groups: %s", strerror(errno));
+        }
+    }
+    
+    ngroups = 0;
+    getgrouplist(pw->pw_name, pw->pw_gid, NULL, &ngroups);
+    
+    groups = malloc(sizeof(gid_t) * ngroups);
+    getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups);
+   
+    for (i = 0; i < ngroups; i++){
+        struct group* gr = getgrgid(groups[i]);
+
+        if(gr == NULL) {
+            free(groups);
+            error("failed to fetch groups: %s", strerror(errno));
+        }
+
+        printf("%s ",gr->gr_name);
+    }
+
+    printf("\n");
+
+    free(groups);
+
+    return EXIT_SUCCESS;
+}