Question

Given a text, $txt, how could I left justify it to a given width in Bash?

Example (width = 10):

If $txt=hello, I would like to print:

hello     |

If $txt=1234567890, I would like to print:

1234567890|

Answer 1

You can use the printf command, like this:

printf "%-10s |\n" "$txt"

The %s means to interpret the argument as string, and the -10 tells it to left justify to width 10 (negative numbers mean left justify while positive numbers justify to the right). The \n is required to print a newline, since printf doesn’t add one implicitly.

Note that man printf briefly describes this command, but the full format documentation can be found in the C function man page in man 3 printf.