myshellin/doc/code/redirection.txt
2021-07-24 12:33:25 -04:00

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typedef struct {
int fd;
int fd_new;
int fd_copy;
char *filename;
int flags;
} Redirect;
Redirect in = {.fd = STDIN_FILENO, .fd_new = -1, .fd_copy = -1, .filename = NULL, .flags = O_RDONLY};
Redirect out = {.fd = STDOUT_FILENO, .fd_new = -1, .fd_copy = -1, .filename = NULL, .flags = O_WRONLY | O_CREAT | O_TRUNC};
Redirect err = {.fd = STDERR_FILENO, .fd_new = -1, .fd_copy = -1, .filename = NULL, .flags = O_WRONLY | O_CREAT | O_TRUNC};
void open_redirect(Redirect *redirect) {
redirect->fd_copy = dup(redirect->fd);
if (redirect->fd_copy == -1) {
perror("dup");
}
else {
redirect->fd_new = open(redirect->filename, redirect->flags, 0664);
if (redirect->fd_new == -1) {
fprintf(stderr, "open: Could not open file %s: \"%s\"\n", redirect->filename, strerror(errno));
}
else {
if (close(redirect->fd) == -1) {
perror("close");
}
if (dup(redirect->fd_new) == -1) {
perror("dup");
}
}
}
}
void close_redirect(Redirect *redirect) {
if (close(redirect->fd_new) == -1) {
perror("close");
}
if (dup2(redirect->fd_copy, redirect->fd) == -1) {
perror("dup2");
}
if (close(redirect->fd_copy) == -1) {
perror("close");
}
}