From 2b3c1171ac6c5da8801897906aeaf0be6428a8ea Mon Sep 17 00:00:00 2001
From: Stefan 'psYchotic' Zwanenburg <stefanhetzwaantje@gmail.com>
Date: Tue, 26 Jan 2010 00:37:18 +0100
Subject: [PATCH] Refactoring:  - The 'cd', 'kill' and 'exit' builtins were
 each extracted to a    function Others:  - Error messages are now printed on
 stderr

---
 ss.c | 117 ++++++++++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 78 insertions(+), 39 deletions(-)

diff --git a/ss.c b/ss.c
index 9de5195..d27df09 100644
--- a/ss.c
+++ b/ss.c
@@ -54,6 +54,80 @@ char **split_input(char *input) {
 }
 
 /**
+ * Exits the shell.
+ * @return non-zero on success (no arguments were passed), zero otherwise.
+ */
+int exit_cmd(char **argv) {
+    if (argv[0] != NULL) {
+        fprintf(stderr, "The 'exit' builtin does not take any arguments.\n");
+        return 0;
+    } else {
+        return 1;
+    }
+}
+
+/**
+ * Sends a signal to a list of PIDs.
+ * In this implementation, the SIGTERM (15) signal is sent. If an error
+ * occurs whilst trying to send said signal, a message is printed on stderr.
+ * Inversely, when sending the signal succeeds, a message is printed on stdout
+ * to notify the user.
+ * @return always zero
+ */
+int kill_cmd(char **argv) {
+    int i;
+    pid_t pid;
+    if (argv[0] == NULL) {
+        printf("The 'kill' builtin takes at least one argument (a PID).\n");
+    } else {
+        for (i = 0; argv[i] != NULL; i++) {
+            if (sscanf(argv[i], "%d", &pid)) {
+                if (kill(pid, SIGTERM)) {
+                    fprintf(stderr, "Couldn't kill the process with PID %d: %s\n", pid, strerror(errno));
+                } else {
+                    fprintf(stderr, "Killed (or sent signal %d) to PID %d.\n", SIGTERM, pid);
+                }
+            } else {
+                printf("%s is not a valid PID. Skipping.\n", argv[i]);
+            }
+        }
+    }
+
+    return 0;
+}
+
+/**
+ * Changes the current working directory.
+ * Note that the actual changing of the current working directory may fail,
+ * in which case an error is printed on stderr. This command takes a single
+ * argument: the directory to change to.
+ * @return always zero
+ */
+int cd_cmd(char **argv) {
+    char *todir;
+    if (argv[0] == NULL) {
+        struct passwd *passwd = getpwuid(getuid());
+        if (passwd == NULL) {
+            fprintf(stderr, "Could not get the current user's home directory: %s\n", strerror(errno));
+        } else {
+            todir = passwd->pw_dir;
+        }
+    } else if (argv[1] == NULL) {
+        todir = argv[0];
+    } else {
+        fprintf(stderr, "The 'cd' builtin takes at most one argument (the directory to move to).\n");
+        return 0;
+    }
+
+    if (chdir(todir)) {
+        fprintf(stderr, "Could not change the current working directory to '%s': %s.\n", todir, strerror(errno));
+    }
+
+    return 0;
+}
+
+
+/**
  * Handles a line of input.
  * This function handles a line of input, which may
  * result in two things:
@@ -79,51 +153,16 @@ int handle_input(char *input) {
         argv = split_input(input);
         free(input);
         if (!strcmp(argv[0], "exit")) {
-            if (argv[1] != NULL) {
-                printf("The 'exit' builtin does not take any arguments.\n");
-            } else {
-                return_value = 1;
-            }
+            return_value = exit_cmd(&argv[1]);
         } else if(!strcmp(argv[0], "kill")) {
-            if (argv[1] == NULL) {
-                printf("The 'kill' builtin takes at least one argument (a PID).\n");
-            } else {
-                for (i = 1; argv[i] != NULL; i++) {
-                    if (sscanf(argv[i], "%d", &pid)) {
-                        if (kill(pid, SIGTERM)) {
-                            printf("Couldn't kill the process with PID %d: %s\n", pid, strerror(errno));
-                        } else {
-                            printf("Killed (or sent signal %d) to PID %d.\n", SIGTERM, pid);
-                        }
-                    } else {
-                        printf("%s is not a valid PID. Skipping.\n", argv[i]);
-                    }
-                }
-            }
+            return_value = kill_cmd(&argv[1]);
         } else if (!strcmp(argv[0], "cd")) {
-            char *todir;
-            if (argv[1] == NULL) {
-                struct passwd *passwd = getpwuid(getuid());
-                if (passwd == NULL) {
-                    printf("Could not get the current user's home directory: %s\n", strerror(errno));
-                } else {
-                    todir = passwd->pw_dir;
-                }
-            } else if (argv[2] == NULL) {
-                todir = argv[1];
-            } else {
-                printf("The 'cd' builtin takes at most one argument (the directory to move to).\n");
-                todir = argv[1] = get_current_dir_name();
-            }
-
-            if (chdir(todir)) {
-                printf("Could not change the current working directory to '%s': %s.\n", todir, strerror(errno));
-            }
+            return_value = cd_cmd(&argv[1]);
         } else {
             pid = fork();
             if (pid == 0) {
                 if (execvp(argv[0], argv)) {
-                    printf("Could not execute '%s': %s\n", argv[0], strerror(errno));
+                    fprintf(stderr, "Could not execute '%s': %s\n", argv[0], strerror(errno));
                 }
                 return_value = 1;
             } else {
-- 
2.11.4.GIT