commit e891693f6f1d939a7d7f744e152f8e3949c3a2b9
Author: Alessandro Mauri <alemauri001@gmail.com>
Date:   Mon Mar 22 14:06:08 2021 +0100

    initial commie

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..f2e841f
--- /dev/null
+++ b/README.md
@@ -0,0 +1 @@
+# US - User Switcher
diff --git a/makefile b/makefile
new file mode 100644
index 0000000..418299e
--- /dev/null
+++ b/makefile
@@ -0,0 +1,25 @@
+CC ?= gcc
+CFLAGS = -Wall -pedantic --std=c99 -O2
+PREFIX = /usr/local
+MANPREFIX = ${PREFIX}/share/man
+
+us: us.c
+
+dbg:
+	gcc -O0 -g us.c -o us
+
+install: us
+	mkdir -p ${DESTDIR}${PREFIX}/bin
+	cp -f us ${DESTDIR}${PREFIX}/bin/us
+	chown root:root ${DESTDIR}${PREFIX}/bin/us
+	chmod 4755 ${DESTDIR}${PREFIX}/bin/us
+#	mkdir -p ${DESTDIR}${MANPREFIX}/man1
+#	cp -f us.1 ${DESTDIR}${MANPREFIX}/man1/us.1
+#	chmod 644 ${DESTDIR}${MANPREFIX}/man1/us.1
+
+uninstall:
+	rm -f ${DESTDIR}${PREFIX}/bin/us
+#		${DESTDIR}${MANPREFIX}/man1/us.1
+
+clean:
+	rm -f us us-dbg
diff --git a/us.c b/us.c
new file mode 100644
index 0000000..342debc
--- /dev/null
+++ b/us.c
@@ -0,0 +1,57 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+
+static void usage (void);
+static int perm_set (uid_t);
+
+int main (int argc, char *argv[])
+{
+	if (argc < 2) {
+		usage();
+		exit(1);
+	}
+
+	uid_t ruid = getuid();
+
+	// Copy argv and argc
+	int c_argc = argc - 1;
+	char **c_argv = malloc((c_argc + 1) * sizeof(char *));
+	if (!c_argv) {
+		fprintf(stderr, "malloc: %s\n", strerror(errno));
+		goto fail_end;
+	}
+	for (int i = 0; i < c_argc; i++)
+		c_argv[i] = strdup(argv[i+1]);
+	c_argc[c_argv] = NULL;
+
+	if (perm_set(0) == -1) { // 0 = root
+		fprintf(stderr, "perm_set: %s\n", strerror(errno));
+		goto fail_end;
+	}
+	if (execvp(*c_argv, c_argv) == -1) // execvp searches in path
+		fprintf(stderr, "execv: %s\n", strerror(errno));
+	// if exec fails reset the permissions
+	if (perm_set(ruid) == -1) { // 0 = root
+		fprintf(stderr, "perm_set: %s\n", strerror(errno));
+		goto fail_end;
+	}
+
+	fail_end:
+	return 0;
+}
+
+static inline void usage (void)
+{
+	printf("usage: us [command]\n");
+}
+
+static inline int perm_set (uid_t id)
+{
+	return seteuid(id);	
+}