First commit of sps(1)

1 files changed, 57 insertions, 0 deletions

diff --git a/cmd.c b/cmd.c
new file mode 100644
index 0000000..b0486a3
--- /dev/null
+++ b/cmd.c
@@ -0,0 +1,57 @@
+#include "sps.h"
+
+/* Process a read line into a command and arguments and try to execute it */
+void cmd(char *line) {
+    char *cmd, *cmd_arg;
+    pid_t pid;
+    int status, cmd_argc;
+    char *cmd_argv[MAX_ARGS];
+    char *cmd_envp[MAX_ENVS];
+
+    /* First argument is always the executable file itself; we make it NULL to
+     * start with, and then terminate the array with NULL */
+    cmd_argv[0] = cmd_argv[1] = NULL;
+    cmd_argc = 1;
+
+    /* Environment is just empty for now, I'll figure this out later */
+    cmd_envp[0] = NULL;
+
+
+    /* Read the command as the first token of the line */
+    cmd = strtok(line, ARG_DELIM);
+
+    /* Iterate through the remaining arguments with subsequent calls to strtok() */
+    while ((cmd_arg = strtok(NULL, ARG_DELIM)) != NULL) {
+        cmd_argc++;
+        if (cmd_argc < MAX_ARGS) {
+            cmd_argv[cmd_argc - 1] = cmd_arg;
+            cmd_argv[cmd_argc] = NULL;
+        }
+    }
+
+    /* If there were too many arguments, say so */
+    if (cmd_argc >= MAX_ARGS) {
+        fprintf(stderr, "Too many arguments (%u given, max is %u)\n", cmd_argc, MAX_ARGS);
+        return;
+    }
+    
+    /* If the command looks to be executable ... */
+    if (access(cmd, X_OK) != -1) {
+
+        /* ... fork and try to execute it; wait until the fork is done. */
+        pid = fork();
+        if (pid == 0) {
+            cmd_argv[0] = cmd;
+            execve(cmd, cmd_argv, cmd_envp);
+        }
+        waitpid(pid, &status, 0);
+
+    /* Otherwise, print an error, because we couldn't find the command */
+    } else {
+        fprintf(stderr, "Command “%s” not found\n", cmd);
+        return;
+    }
+
+    return;
+}
+