vlajos/misspell-fixer

var is referenced but not assigned.

Problematic code:

var=name
n=42
echo "$var_$n.jpg"   # overextended

or

target="world"
echo "hello $tagret"  # misspelled

or

echo "Result: ${mycmd -a myfile}"  # trying to execute commands

Correct code:

var=name
n=42
echo "${var}_$n.jpg"

or

target="world"
echo "hello $target"

or

echo "Result: $(mycmd -a myfile)"

Rationale:

ShellCheck has noticed that you reference a variable that is not assigned. Double check that the variable is indeed assigned, and that the name is not misspelled.

Note: This message only triggers for variables with lowercase characters in their name (foo and kFOO but not FOO) due to the standard convention of using lowercase variable names for unexported, local variables.

Exceptions:

ShellCheck does not attempt to figure out runtime or dynamic assignments like with source "$(date +%F).sh" or eval var=value.

If you know for a fact that the variable is set, you can use ${var:?} to fail if the variable is unset (or empty), or explicitly initialize/declare it with var="" or declare var. You can also disable the message with a [[directive]].

Notice

Original content from the ShellCheck https://github.com/koalaman/shellcheck/wiki.

Shells disambiguate $(( differently or not at all. If the first $( should start command substitution, add a space after it.

Problematic code:

echo "$((cmd "$@") 2>&1)"

Correct code:

echo "$( (cmd "$@") 2>&1)"

Rationale:

You appear to be using $(( with two (or more) parentheses in a row, where the first $( should open a subshell.

This is an ill-defined structure that is parsed differently between different shells and shell versions. Prefer adding spaces to make it unambiguous, both to shells and humans.

Consider the $((( in $(((1)) ):

Ash, dash and Bash 1 parses it as $(( ( and subsequently fail to find the matching )). Zsh and Bash 2+ looks ahead and parses it as $( ((. Ksh parses it as $( ( (.

Exceptions:

Alternatively, you may indeed have correctly spaced your parentheses, but ShellCheck failed to parse $(( as an arithmetic expression while accidentally succeeding in parsing it as $( + (.

In these cases, double check the syntax to ensure ShellCheck can parse the $((, or ignore this error and hope that it won't affect analysis too severely.

Notice

Original content from the ShellCheck https://github.com/koalaman/shellcheck/wiki.

Tips depend on target shell and yours is unknown. Add a shebang.

Problematic code:

echo "$RANDOM"   # Does this work?

Correct code:

#!/bin/sh
echo "$RANDOM"  # Unsupported in sh. Produces warning.

or

#!/bin/bash
echo "$RANDOM"  # Supported in bash. No warnings.

Rationale:

Different shells support different features. To give effective advice, ShellCheck needs to know which shell your script is going to run on. You will get a different numbers of warnings about different things depending on your target shell.

ShellCheck normally determines your target shell from the shebang (having e.g. #!/bin/sh as the first line). The shell can also be specified from the CLI with -s, e.g. shellcheck -s sh file.

If you don't specify shebang nor -s, ShellCheck gives this message and proceeds with some default (bash).

Note that this error can not be ignored with a [[directive]]. It is not a suggestion to improve your script, but a warning that ShellCheck lacks information it needs to be helpful.

Exceptions

None. Please either add a shebang or use -s.

Notice

Original content from the ShellCheck https://github.com/koalaman/shellcheck/wiki.