I am trying to implement a program that takes in a process followed by a string consisting of pipeline commands. How do I separate the string of commands, into {individual command/any number of arguments arrays} The "|" is the character that separates the different commands.
For instance, if I put: pipe ls -lt | cat Lebowski | cd .. .
How would i get the system to recognize that there are three separate command line arguments here to be represented in different pipes.
First of all since pipe is a special symbol you need to escape it when passing to a program:
pipe ls -lt \| cat Lebowski \| cd .. .
in your main function:
main(int argc, char *argv[]) {
the argv contains all these arguments (ls, -lt, |, cat...) at different indices. For example, argv[0] is ls, argv[2] is '|'. argc is the total number of such arguments.
perreal's answer is very good if you want to do this yourself. There is a function getopt() which you can use for this purpose as well and is documented here getopt()
The strtok_r() function is your friend:
char **explode(char *s, const char *sep, size_t *outsz)
{
size_t allocsz = 4;
size_t sz = 0;
char **arr = malloc(allocsz * sizeof(*arr));
if (arr == NULL) {
*outsz = 0;
return NULL;
}
char *p, *end;
for (p = srtok_r(s, sep, &end); p; p = strtok_r(NULL, sep, &end)) {
if (++sz > allocsz) {
allocsz <<= 1;
arr = realloc(arr, sizeof(*arr) * allocsz));
assert(arr != NULL); // sorry
}
arr[sz - 1] = strdup(p);
}
*outsz = sz;
return arr;
}
Usage:
int main()
{
char sentence[] = "The quick brown fox jumped over the lazy dog.";
size_t sz;
char **arr = explode(sentence, " ", &sz);
int i;
for (i = 0; i < sz; i++) {
printf("%s\n", arr[i]);
free(arr[i]);
}
free(arr);
return 0;
}
Since | is a special character to most common shells, you need to quote them (as others have stated). If you quote all the arguments inside of double-quotes such as
pipe "ls -lt | cat Lebowski | cd .. "
You can parse argv[1] with strtok_r().
strtok