with

Construct context aware function on top of L_finally.

The with module implements the RAII (Resource Acquisition Is Initialization) pattern for Bash. It allows you to acquire resources (change directory, create temporary files) that are automatically cleaned up when the current function returns, regardless of how it exits (return or error).

Usage Guide

Changing Directory (L_with_cd)

Use L_with_cd to temporarily change the current working directory. The original directory is restored automatically when the function returns.

my_function() {
    # Change to /tmp
    L_with_cd /tmp

    # Do work in /tmp
    pwd 

    # When my_function returns, we automatically cd back to where we started.
}

Temporary Files (L_with_tmpfile_to)

Create a temporary file that is automatically deleted when the function returns.

process_data() {
    local temp_file
    # Create temp file and store path in 'temp_file'
    L_with_tmpfile_to temp_file

    echo "some data" > "$temp_file"
    process "$temp_file"

    # temp_file is removed automatically here
}

Temporary Directories (L_with_tmpdir_to, L_with_cd_tmpdir)

You can create a temporary directory or create it and immediately cd into it.

# Create a temp dir, use it, and have it removed automatically
use_temp_dir() {
    local dir
    L_with_tmpdir_to dir
    touch "$dir/file1"
}

# Create a temp dir, cd into it, and have it removed and cwd restored automatically
work_in_isolation() {
    L_with_cd_tmpdir
    # Now in a fresh empty directory in /tmp
    echo "stuff" > data.txt
    # On return: cd back to original dir, and remove the temp dir.
}

Redirecting Stdout to Variable (L_with_redirect_stdout_to)

This function allows you to capture the standard output of the current function into a variable. It avoids the performance penalty and subshell isolation of $(...).

Important: The capture happens when the function returns. Therefore, the target variable must be visible after the function returns (e.g., a global variable, or a local variable in the calling function, or a nameref).

# Capture stdout of this function into the variable named by $1
get_config_data() {
    # $1 is the name of the variable to store result in
    L_with_redirect_stdout_to "$1"

    echo "key=value"
    echo "status=ok"
}

main() {
    local result
    get_config_data result
    echo "Got: $result"
}

API Reference

with

What we can do with finally? We can do destructors.

L_with_cd

Change to given directory.

Register RETURN trap for parent function that will restore current working directory.

Arguments:

• $1 Directory to cd into.
• $2 Optional stack offset to add to RETURN trap.

L_with_tmpfile_to

Create a temporary directory.

Register RETURN trap for parent fuction that will remove the directory.

Arguments:

• $1 Variable to assign the temporary file to.
• $2 Optional stack offset to add to RETURN trap.

L_with_tmpdir_to

Create a temporary directory.

Register RETURN trap for parent fuction that will remove the directory.

Arguments:

• $1 Variable to assign the temporary directory location to.
• $2 Optional stack offset to add to RETURN trap.

L_with_cd_tmpdir

Create a temporary directory and cd into it.

Register RETURN trap that will remove the temporary directory and restore working directory on return from parent function.

Argument: $2 Optional stack offset to add to RETURN trap.

L_with_process

Run command in background and store its PID in variable.

Register RETURN trap that will kill process on return from parent function.

Options:

• -v Be verbose.
• -h Show help.

Arguments:

• $1 Variable to store the PID of the background process.
• $@ Command to execute in the background.

L_with_redirect_stdout_to

Temporary redirect stdout to string.

Non-forking command substition for the poor.

Arguments:

• $1 Variable to capture stdout to.
• $2 Optional stack offset to add to RETURN trap.