Question

How can I remove the ‘\n’ from each string in this array?

I know that I can do something like this for a simple C-String, but I failed at using it in this case

cmd[strcspn(cmd, "\n")] = '\0';

I am also not sure if that would be the propper way or not.

The String will never contain any space or \n in the middle. They are also of a static length (6).

#include <stdlib.h>

unsigned char cmd[][6] = { 
    {"r123\n"},
    {"r999\n"},
    {"l092\n"},
    {"l420\n"}};

void main(void) {
    int i;

    for(i = 0; i < (sizeof(cmd) / sizeof(cmd[0])); i++) {
        printf("%s\n", cmd[i]);
    }   
}

Answer 1

Just do it by hand, it’s easy!

If it’s guaranteed to be only the last char in every word, and it’s guaranteed to be there, than like this:

for (i = 0; i < elem_number; ++i){
    cmd[i][strlen(cmd[i])-1] = 0;
}

If, on the other hand, you are unsure how many whitespace characters there will be at the end, but you know they will only be there at the end (there might be 0 in this case!) than this:

for (i = 0; i < elem_number; ++i){
    for (j = 0; cmd[i][j] != 0; ++j){
        if (isspace(cmd[i][j]))
             cmd[i][j] = 0;
     }
}

Voila!

If there will be whitespaces in the middle, then you have to define the desired behaviour: cut only the trailing whitespaces, cut the string in many little ones, or something completely different.

Oh, and one other sidenote:
everyone else seems to be using char = '\0'. In C, '\0' and 0 are equivalent, i.e. if ('\0' == 0) { ... } evaluates to true.

Sidenote 2: I used elem_number because I did not know if the number of elements is a parameter or hardcoded / know in advance. Substitute with what is appropriate.