Description: Nohup is a POSIX command that allows a command to continue running in the background after the user has logged out. Its name comes from the combination of ‘no hang up’, meaning that the process will not be affected by the SIGHUP signal, which is sent to processes when the terminal closes. This command is especially useful in various environments, where users may start long-running processes and do not want them to be interrupted when logging out. Nohup automatically redirects standard output and error to a file called ‘nohup.out’, unless specified otherwise. This allows users to review the results of the command execution later. In systems using various shell environments, Nohup integrates seamlessly, enabling users to run background tasks efficiently and effortlessly. Its simplicity and effectiveness have made it an essential tool for system administrators and developers working in command-line environments.
History: The Nohup command was introduced in Unix systems in the 1970s as part of the evolution of process management in command-line environments. Its development is framed within the need to allow processes to continue running independently of the user’s session, which became crucial as systems grew more complex and users began performing longer and more demanding tasks. Over the years, Nohup has been adopted in various Unix variants and Unix-based operating systems, such as Linux and macOS, establishing itself as a standard tool in system administration.
Uses: Nohup is primarily used in server environments and situations where users need to run long-duration processes without worrying about their interruption. It is commonly employed to run maintenance scripts, backup tasks, or any process that requires considerable time to complete. Additionally, it is useful in situations where users want to start background processes and continue working on other tasks without having to monitor the execution of the initial command.
Examples: A practical example of using Nohup would be running a Python script that performs extensive data analysis. The command could be: ‘nohup python3 analisis_datos.py &’. This would allow the script to run in the background, and the user could log out without stopping the process. The output of the script would be saved in ‘nohup.out’, allowing the user to review the results later. Another example would be starting a web server in the background with: ‘nohup python3 -m http.server 8000 &’.
