Looping without brace expansion

Question

I'm using a blackbox CLI based on Bash and I'm not entirely sure what stuff I can use. Brace expansion doesn't work, and with it goes my ability to do loops without listing the arguments explicitly, which is something I was trying to avoid by looping to start with.

for x in {1..5}
do
    for y in {a..c}
    do
    echo $HOME$x$y
    done
done

How do I run something like this without brace expansion and without listing the arguments explicitly? Environment variables should also work, that's why I appended a random $HOME to the example.

Please feel free to provide different alternatives (AWK, sed) as I'm not entirely sure what will and what won't work.

Answer 1

You'd better use jot as commented. Here is a (not so pretty) awk implementation.

#!/usr/bin/awk -f
BEGIN{
    for(i=1;i<5;i++)
        for(j=97;j<100;j++)
            printf "%s%d%c ",ENVIRON["HOME"],i,j;                               
    print;
}

or (you may also use the -v option of awk to assign shell variables to awk variables)

#!/bin/bash
awk -f /dev/fd/3 3<< EOF                                                                                                                                                                                    
BEGIN{
    for(i=1;i<5;i++)
        for(j=97;j<100;j++)
            printf "$HOME%d%c ",i,j;
    print;
}
EOF

Answer 2

If you're sure you run bash, maybe brace expansion isn't enabled.

Check it with by using

echo $-
himBHs

In the shell I'm using, the option B is set, indicating that brace expansion is enabled.

You can set the brace expansion by using one of these commands:

set -o braceexpand
set -B

In this case I don't need to loop over the letter or numbers:

echo {1..5}{a..c}
1a 1b 1c 2a 2b 2c 3a 3b 3c 4a 4b 4c 5a 5b 5c

or disable it by using either

set +o braceexpand
set +B

leading to

echo {1..5}{a..c}
{1..5}{a..c}