Execute a Command in Multiple Directories on Linux

As a Linux user, it's common to run the same command in multiple directories. For example, you might want to search for all files with a certain extension or run a shell script in multiple directories. This task can be time-consuming if done manually, and becomes even more tedious as the number of directories increases. Fortunately, Linux provides several methods for running a command across multiple directories efficiently.

Using the Find Command to Execute Commands

The find command is one of the most powerful commands available in Linux. It allows you to search files and directories based on different criteria like name, size, date, etc. You can also execute commands on the files and directories found by the find command using the -exec option.

Example Execute Command on Files

find /path/to/directories -type f -name "*.txt" -exec cat {} \;

This command searches for all '.txt' files in directories at "/path/to/directories" and runs the cat command on each. The {} represents the file found, and \; indicates the end of the command to execute.

This is the contents of file1.txt
This is the contents of file2.txt  
This is the contents of file3.txt

Example Execute Command in Each Directory

find /path/to/parent -type d -exec sh -c 'cd "{}" && ls -la' \;

This executes ls -la in each subdirectory found.

Using the xargs Command

The xargs command executes commands using input from another command. It's particularly useful when combined with find to process multiple directories efficiently.

Example Process Multiple Files

find /path/to/directories -name "*.txt" | xargs cat

This finds all .txt files and passes them to cat for processing.

Example Execute in Multiple Directories

find /path/to/parent -type d | xargs -I {} sh -c 'cd "{}" && pwd && ls'

The -I {} option allows you to specify where the input should be placed in the command.

Using a For Loop

A simple for loop can iterate through directories and execute commands in each one.

for dir in /path/to/directories/*/; do
    cd "$dir"
    echo "Processing directory: $dir"
    ls -la
    cd -
done

This script changes to each directory, executes commands, then returns to the original location with cd -.

Using a Shell Script

For more complex operations, create a dedicated shell script that can be reused and customized.

#!/bin/bash

# Script to execute commands in multiple directories
PARENT_DIR="/path/to/directories"
COMMAND="ls -la"

for dir in "$PARENT_DIR"/*/; do
    if [ -d "$dir" ]; then
        echo "Executing in: $dir"
        cd "$dir"
        eval "$COMMAND"
        cd - > /dev/null
        echo "---"
    fi
done

This script is more robust, checking if each item is actually a directory before processing.

Comparison of Methods

Key Points

• Use find -exec for file-based operations with complex search criteria

• Use xargs when processing large numbers of files or directories

• Use for loops for simple directory iteration tasks

• Always quote variables containing paths to handle spaces correctly

• Test commands on a small subset before running on all directories

Conclusion

Running commands across multiple directories is a common Linux task that can be accomplished efficiently using find, xargs, for loops, or shell scripts. Each method has its strengths choose based on your specific needs and complexity requirements. These techniques will save significant time and reduce manual effort in directory operations.