如何在Bash脚本中展开含方括号数字范围的参数？

It sounds like you're trying to parse and expand range-based arguments (like node-[2,5-7,10-13]) into individual items within your script. Here's a step-by-step solution using bash, focusing on safety and clarity:

Step 1: Extract the prefix and range components #

First, split your input argument into the base prefix (e.g., node-) and the range string inside the brackets:

#!/bin/bash

# Capture the input argument (e.g., "node-[2,5-7,10-13]")
input="$1"

# Extract everything before the opening bracket as the prefix
prefix=$(echo "$input" | sed -E 's/\[.*\]$//')

# Extract the content inside the brackets as the range string
range_str=$(echo "$input" | sed -E 's/.*\[([^\]]+)\]$/\1/')

Step 2: Convert ranges to bash brace expansion format #

Bash uses .. for continuous ranges in brace expansion, so we'll replace hyphens in our range string with this syntax:

# Replace "-" with ".." to match bash's brace expansion rules
brace_range=$(echo "$range_str" | sed 's/-/../g')

# Build the full brace pattern (e.g., "node-{2,5..7,10..13}")
expanded_pattern="${prefix}{$brace_range}"

Step 3: Expand the pattern into a list of items #

Now we can turn this brace pattern into an array of individual items. This method is safe for trusted input:

# Expand the pattern and store it in an array
nodes_array=($expanded_pattern)

Step 4: Iterate over the items #

You can now loop through the array to process each node:

# Loop through each expanded node item
for node in "${nodes_array[@]}"; do
    echo "Processing: $node"
    # Add your custom logic here (e.g., connect to the node, run commands)
done

Security Note #

If your script accepts input from untrusted sources, directly expanding brace patterns can pose a security risk (potential code injection). Add input validation to ensure the range string only contains allowed characters:

# Validate the range string (only digits, commas, and hyphens are permitted)
if ! [[ "$range_str" =~ ^[0-9,-]+$ ]]; then
    echo "Error: Invalid range format. Only digits, commas, and hyphens are allowed."
    exit 1
fi

Example Usage #

Running ./myscript node-[2,5-7,10-13] will output:

Processing: node-2
Processing: node-5
Processing: node-6
Processing: node-7
Processing: node-10
Processing: node-11
Processing: node-12
Processing: node-13

An alternative (but not recommended for untrusted input) is using eval, which executes arbitrary shell code:

# Avoid this if input comes from untrusted sources!
eval "nodes_array=($expanded_pattern)"

Content of the question originates from Stack Exchange, asked by Renat