add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/id.c

@@ -0,0 +1,52 @@
+/* id - return uid and gid		Author: John J. Marco */
+
+
+/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
+/* 		----- id.c -----					*/
+/* Id - get real and effective user id and group id			*/
+/* Author: John J. Marco						*/
+/*	   pa1343@sdcc15.ucsd.edu					*/
+/*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*/
+
+#include <sys/types.h>
+#include <pwd.h>
+#include <grp.h>
+#include <stdio.h>
+
+main()
+{
+  struct passwd *pwd;
+  struct passwd *getpwuid();
+  struct group *grp;
+  struct group *getgrgid();
+  int uid, gid, euid, egid;
+
+  uid = getuid();
+  gid = getgid();
+  euid = geteuid();
+  egid = getegid();
+
+  if ((pwd = getpwuid(uid)) == (struct passwd *) NULL)
+	printf("%s%d%s", "uid=", uid, " ");
+  else
+	printf("%s%d%s%s%s", "uid=", uid, "(", pwd->pw_name, ") ");
+
+  if ((grp = getgrgid(gid)) == (struct group *) NULL)
+	printf("%s%d%s", "gid=", gid, " ");
+  else
+	printf("%s%d%s%s%s", "gid=", gid, "(", grp->gr_name, ") ");
+
+  if (uid != euid)
+	if ((pwd = getpwuid(euid)) != (struct passwd *) NULL)
+		printf("%s%d%s%s%s", "euid=", euid, "(", pwd->pw_name, ") ");
+	else
+		printf("%s%d%s", "euid=", euid, " ");
+
+  if (gid != egid)
+	if ((grp = getgrgid(egid)) != (struct group *) NULL)
+		printf("%s%d%s%s%s", "egid=", egid, "(", grp->gr_name, ") ");
+	else
+		printf("%s%d%s", "egid=", egid, " ");
+
+  printf("\n");
+}