According to the subject commands are separated by ";" or "|".
Microshell scans its arguments (char **av).
If there are no two arguments (*av && *(av + 1)) returns zero, otherwise
skips the first one av++; and looks for ";" or "|" while (av[i] && strcmp(av[i], "|") && strcmp(av[i], ";")) i++; .
Once a separator is found, there is something to execute.
If it is a change directory command (!strcmp(*av, "cd")) returns the exit status of cd builtin execution.
if (i == 0) means that *av was void. there is nothing to do. Otherwise, it returns the exit status of executor execution.
Advances av pointer the number i of arguments till separator. av += i.
Only cd can be executed, so if (i != 2) it is an error.
if the change directory execution is wrong (chdir(av[1]) == -1) shows a message.
Gets a pointer to the arguments list av and the number of arguments till the separator i .
Checks (av[i] %% !strcmp(av[i], "|")) if the separator exists and it is a pipe.
If it is a pipe, create the pipe ((pipe(fd) == -1) , printing an error if fails.
Forks the process. child and father, when there is a pipe, duplicate standard input/output.
Child duplicates standard output dup2(fd[1], 1) and closes both sides of pipe.
Child executes execve(). if everything is ok, finish here. The child's return only happens when execve() was wrong.
Father waits child termination with waitpid(pid, &status, 0) .
Father duplicates standard input dup2(fd[0], 0) and closes both sides of pipe.
father returns child execution status detected with (WIFEXITED(status) && (WEXITSTATUS(status)).
Aside from writing in stderr (2), returns 1, reporting an error status.
Test it with bash make test.
There is a Makefile in folder tests to launch two .sh scripts.