static void
set_logging_on (char *args, int from_tty)
{
char *rest = args;
if (rest && *rest)
{
xfree (logging_filename);
logging_filename = xstrdup (rest);
}
handle_redirections (from_tty);
}
/* This procedure forks off a child process to execute the command
stored in com, which it takes as an argument */
void execute_com(Command *com){
int fork_ret;
int exec_ret;
fork_ret = fork();
if (fork_ret == 0){
handle_redirections(com);
exec_ret = execvp(com->command, com->args);
fprintf(stderr, "%s: ", com->command);
perror(NULL);
exit(1);
} else{
if (com->wait){
while (1){
if (wait(&exec_ret) == fork_ret) break;
}
}
}
return;
}
/* This procedure takes a Pipe_Command * as an argument and executes
the Pipe Command. It uses two pipes (pidefda and pipefdb) to facilitate
I/O redirection in commands containing multiple pipes. */
void exec_pip_com(Pipe_Command *pip_com){
int i; /* Arbitrary iteration variable */
int fork_ret; /* Return of a fork() call */
int exec_ret; /* Passed to wait() */
int pipefda[2]; /* I/O descriptors for "pipe A" */
int pipefdb[2]; /* I/O descriptors for "pipe B" */
char pipe_in_use; /* 'a' or 'b' for pipe that is in use */
pipe_in_use = 'b';
for (i = 0; i < pip_com->num_commands; i++){
/* Create Pipe between processes. Initialize pipefda or pipefdb,
depending on which connected the current process and the previuos
one. */
if (i < pip_com->num_commands - 1){
if (pipe_in_use == 'a'){
if (pipe(pipefdb) < 0){
perror("Pipe Initialization failed.\n");
exit(1);
}
pipe_in_use = 'b';
} else{
if (pipe(pipefda) < 0){
perror("Pipe Initialization failed.\n");
exit(1);
}
pipe_in_use = 'a';
}
}
/* Fork off child for executing shell command */
fork_ret = fork();
if (fork_ret == 0){ /* In execution of child process. */
if (i == 0){ /* Handle execution of first command. */
/* Dup stdout to write end of first pipe. Close the
necessary file descriptors and execute command. */
handle_redirections(pip_com->commands[i]);
if (dup2(pipefda[1], 1) != 1){
perror("Error duping pipefda[1]\n");
exit(1);
}
close(pipefda[1]);
close(pipefda[0]);
execvp(pip_com->commands[i]->command, pip_com->commands[i]->args);
fprintf(stderr, "%s: ", pip_com->commands[i]->command);
perror(NULL);
exit(1);
} else if (i == pip_com->num_commands - 1){ /* Handle execution of last command */
/* Dup stdin to read end of final pipe. Close the
necessary file descriptors and execute command. */
handle_redirections(pip_com->commands[i]);
if (pipe_in_use == 'a'){
if (dup2(pipefda[0], 0) != 0){
perror("Error duping pipefda[0]\n");
exit(1);
}
close(pipefda[0]);
close(pipefda[1]);
} else{
if (dup2(pipefdb[0], 0) != 0){
perror("Error duping pipefdb[0]\n");
exit(1);
}
close(pipefdb[0]);
close(pipefdb[1]);
}
execvp(pip_com->commands[i]->command, pip_com->commands[i]->args);
fprintf(stderr, "%s: ", pip_com->commands[i]->command);
perror(NULL);
exit(1);
}
else{ /* Handle execution of middle commands */
if (pipe_in_use == 'a'){ /* 'A' is the new pipe */
/* Dup stdout to write end of new pipe. */
if (dup2(pipefda[1], 1) != 1){
perror("Error duping pipefda[1]\n");
exit(1);
}
/* Dup stdin to read end of old pipe. */
if (dup2(pipefdb[0], 0) != 0){
perror("Error duping pipefdb[0]\n");
exit(1);
}
/* Close both file descriptors */
close(pipefda[1]);
close(pipefdb[0]);
} else{ /* 'B' is the new pipe */
/* Dup stdout to write end of new pipe. */
if (dup2(pipefdb[1], 1) != 1){
perror("Error duping pipefdb[1]\n");
exit(1);
}
/* Dup stdin to read end of old pipe. */
if (dup2(pipefda[0], 0) != 0){
perror("Error duping pipefda[0]\n");
exit(1);
}
/* Close both file descriptors */
close(pipefdb[1]);
close(pipefda[0]);
}
/* Execute command, exit if error occurs */
execvp(pip_com->commands[i]->command, pip_com->commands[i]->args);
fprintf(stderr, "%s: ", pip_com->commands[i]->command);
perror(NULL);
exit(1);
}
} else{
/* Back in execution of parent process. */
/* Close write end of pipe for first command in pipe */
if (i == 0){
close(pipefda[1]);
if (pip_com->wait){
while(1){
if (wait(&exec_ret) == fork_ret) break;
}
}
} else if (i == pip_com->num_commands - 1){
/* Close read end of pipe for last command in pipe */
if (pip_com->wait){
while(1){
if (wait(&exec_ret) == fork_ret) break;
}
}
if (pipe_in_use == 'a'){
close(pipefda[0]);
} else{
close(pipefdb[0]);
}
} else{
/* Close read end of pipe for previous pipe
Close write end of pipe for new pipe */
if (pipe_in_use == 'a'){
close(pipefda[1]);
if (pip_com->wait){
while(1){
if (wait(&exec_ret) == fork_ret) break;
}
}
close(pipefdb[0]);
} else{
close(pipefdb[1]);
if (pip_com->wait){
while(1){
if (wait(&exec_ret) == fork_ret) break;
}
}
close(pipefda[0]);
}
}
}
}
return;
}