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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <string.h>
struct item {
char *prog_name;
int pid;
struct item *next;
};
static int check_delimiter(char *arg)
{
return !strncmp(arg, ";;", 3);
}
static void fill_in_item(char *arg, int pid, struct item **list)
{
struct item *tmp_item = malloc(sizeof(struct item));
tmp_item->pid = pid;
tmp_item->prog_name = arg;
tmp_item->next = *list;
*list = tmp_item;
}
static void make_new_fork(int fd[2], char **begin_pos, struct item **list,
int *process_counter)
{
static int first_process_flag = 0;
int pid = fork();
if(pid == -1) {
perror("fork error");
exit(1);
}
if(pid) {
fill_in_item(*begin_pos, pid, list);
++*process_counter;
} else {
/* first process writes to pipeline */
if(first_process_flag == 0) {
close(fd[0]);
dup2(fd[1], 1);
close(fd[1]);
/* second process reads */
} else {
close(fd[1]);
dup2(fd[0], 0);
close(fd[0]);
}
execvp(*begin_pos, begin_pos);
perror(*begin_pos);
exit(1);
}
++first_process_flag;
}
static char* find_name_by_pid(int pid, struct item *list)
{
while(list) {
if(list->pid == pid)
return list->prog_name;
list = list->next;
}
return NULL;
}
static void clear_list(struct item *list)
{
struct item *tmp;
while(list) {
tmp = list;
list = list->next;
free(tmp);
}
}
int main(int argc, char **argv)
{
int fd[2];
int status, pid, process_counter;
char **begin_pos, **end_pos;
struct item *list = NULL;
process_counter = 0;
pipe(fd);
if(argc == 1) {
fprintf(stderr, "too few arguments\n");
return 1;
}
++argv;
for(begin_pos = argv, end_pos = begin_pos + 1; *end_pos != NULL; ) {
if(check_delimiter(*end_pos)) {
*end_pos = NULL;
make_new_fork(fd, begin_pos, &list, &process_counter);
begin_pos = end_pos + 1;
end_pos = begin_pos + 1;
} else
++end_pos;
}
make_new_fork(fd, begin_pos, &list, &process_counter);
close(fd[0]);
close(fd[1]);
for( ; process_counter; --process_counter) {
pid = wait(&status);
if(WIFEXITED(status) && WEXITSTATUS(status) == 0)
printf("%s\n", find_name_by_pid(pid, list));
}
clear_list(list);
return 0;
}
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