Bash Parameter Expansion
Enter literal variable values and evaluate one parameter expression without running commands.
A QUICK WALKTHROUGH
How to use this tool
- Enter one NAME=value per line; omit a name to leave it unset.
- Enter one expression such as ${file##*/}.
- Expand and review the result and current variable values.
Supported expressions
Supports ${name}, ${#name}, default/alternate/assignment/error operators, integer substrings, prefix/suffix removal, replacement, and ASCII case conversion. Patterns support only * and ?. Replacement patterns must match at least one character.
Scope and limits
This is a static parameter-expression simulator, not a shell. No command, arithmetic, process or nested substitution; arrays, quoting, escape syntax, bracket patterns, tilde expansion, word splitting and filesystem expansion are unsupported. Variable values are literal text, including quotes and dollar signs. Replacement values are literal; & is rejected.
GOOD TO KNOW
Common questions
Are commands executed?
No. Only entered variables are used. Nothing reads system variables or files, and data is not uploaded.
Does assignment persist?
The = and := operators update the displayed variables for that calculation only. Copy them into the input for another calculation.