Question

I want to know if there is a built-in BASH command that prints some text on stderr, just like the echo command that prints text on stdout. I don’t want to use temporary io-redirection. I use a built-in command to generate an error on stderr such as ls --asdf (ls: unrecognized option ‘–asdf’) but I want something neater.

Edit —-

Actually I am trying to demonstrate stderr/stdout redirection, and my example looks like:

sh test.sh >test-out.txt 2>test-err.txt

For clarity, I want to keep the test.sh file as simple and clean as possible, this means avoiding > operator inside the file.

Answer 1

echo something >&2 is the correct way to do what you want.

However…

This will create a little program that will echo its arguments to stderr:

gcc -o echoerr -x c - <<'EOF'
#include <stdio.h>
#include <stdlib.h>
void main(int argc, char **argv) {
    int i;
    for (i = 1; i < argc; i++) {
        fprintf(stderr, "%s ", argv[i]);
    }
    fprintf(stderr, "\n");
    exit(0);
}
EOF

You can use it like this:

$ ./echoerr this is an error message
this is an error message
$ ./echoerr this is an error message 2>error.out
$ cat error.out
this is an error message