In Linux systems, the & symbol is a very useful tool for running tasks in the background. It allows you to continue executing other operations in the terminal while performing long-running tasks. Today, we will learn about this super practical symbol—&.1. What is the & Symbol?The & symbol is used in the Linux command line to run tasks in the background. When you add & at the end of a command, that command will execute in the background without blocking the current terminal session. This is very useful for executing long-running tasks, such as downloading files or compiling code.2. Usage of &Basic command format:
command & # Run the command in the background.Common operations:View background tasks: Use the jobs command to view background tasks in the current session.Bring a background task to the foreground: Use the fg command to bring a background task to the foreground.Send a foreground task to the background: Use Ctrl+Z to pause the current task, then use the bg command to send it to the background.3. Example OperationsExample 1: Running a task in the background
sleep 100 & # This command will run sleep 100 in the background, # the terminal will return immediately, allowing you to execute other commands.Example 2: Viewing background tasks
jobs # This command will list all background tasks in the current session.Example 3: Bringing a background task to the foreground
fg %1 # This command will bring the background task with job number 1 to the foreground.Example 4: Sending a foreground task to the background
Ctrl+Z bg %1 # First press Ctrl+Z to pause the currently running command, then use the bg command to send it to the background.4. Practical TipsScenario 1: Running multiple tasks simultaneouslyYou can run multiple tasks simultaneously and send them to the background:
sleep 100 & sleep 200 & # These two tasks will run simultaneously in the background.Scenario 2: Redirecting output of background tasksTo avoid the output of background tasks interfering with the terminal, you can redirect the output to a file:
sleep 100 > output.txt 2>&1 & # This command redirects the output of sleep 100 to output.txt and runs it in the background.5. PrecautionsTask management: Use the jobs command to view background tasks in the current session, and use fg and bg commands to switch tasks between foreground and background.Signal handling: Commands running in the background may be affected by signals such as SIGTERM or SIGKILL. Ensure your commands can handle these signals correctly.Task termination: You can use the kill command to terminate background tasks:
kill %1 # This command will terminate the background task with job number 1.6. Interactive SectionQuestion 1: How do you run a task in the background and check its status?Question 2: When using the & symbol, how do you bring a background task back to the foreground?If you already know the answers, or if you have other questions about using the & symbol, feel free to leave a comment for discussion! Let’s communicate and improve together.