Parameter expansion in Bash

The brace toolkit: length, trims, defaults and substitution.

file="report.draft.txt"

echo "${#file} characters"          # length
echo "${file%.txt}"                 # strip the shortest suffix match
echo "${file%%.*}"                  # strip the longest suffix match
echo "${file#report.}"              # strip a prefix

# defaults: use a fallback without touching the variable
echo "${EDITOR_CHOICE:-nano}"
echo "${file/draft/final}"          # substitution
echo "${file^^}"                    # uppercase

How it works

${#file} is length; % and # trim suffixes and prefixes.
:- supplies a default without touching the variable.
${file/draft/final} substitutes; ^^ uppercases.

Keywords and builtins used here

echo

The run, in numbers

Lines: 11
Characters to type: 448
Tokens: 61
Three-star pace: 70 tpm

At the three-star pace of 70 tokens a minute, this run takes about 52 seconds.

Type this snippet

Step 2 of 3 in Variables & quoting, step 2 of 26 in Language basics.

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