Linux

A log file can hold more lines than you can scan by eye when you need to find an error message. grep is a command-line tool that searches text and prints the lines that match. I’ll show you how to search a file with grep and read its matches and exit status. TL;DR: Search for

When a Linux machine seems short on memory, a terminal snapshot can show how much RAM and swap are in use. The free command reports those figures and estimates how much memory is available to new applications. This article explains how to read the free and available figures and how to take a short series

Composing a message or checking local mail from a Linux terminal starts with knowing what the mail command can do on your system. The Linux mail command is a terminal client for writing messages and reading the current user’s local mailbox. I’ll show how to check which mail implementation is installed and use GNU Mailutils

Software installation instructions can ask which Linux distribution and release is installed, while other checks need the kernel release instead. Linux version commands show either the installed distribution’s release or the running kernel’s release. I’ll show how to read the distribution release from /etc/os-release and check the kernel release separately. TL;DR: Find the Linux distribution

Terminal checks can go stale while you read their output. The Linux watch command reruns a command at intervals and displays its current output in a terminal. In this piece, I’ll show you how to set a refresh interval and watch the output of a command pipeline. TL;DR The Linux watch command runs a command

Before checking filesystem free space, you may first want to know how much space a particular directory uses. The du command estimates the space used by that directory and its contents. I’ll explain what du measures and show how to request a total or inspect another directory level. TL;DR Use the readable-units option with a

At a Linux terminal, the right password command depends on whose account needs a change. passwd updates the password for your account or for another account when you name it. I’ll explain which passwd command to use for your own account or another user’s, and how to handle password-change errors and related tasks. TL;DR: Change

After a command is installed, its name may be clear while the executable’s location is not. The which command searches directories in PATH, the list of places used to find commands, and prints the path of a matching executable. You’ll learn how to look up a command and what to check when which prints no

An unfamiliar directory can contain several layers of folders, making its contents harder to scan. The tree command displays those folders and their files in a branching hierarchy. This article covers installing tree and tailoring its output with depth limits and name filters. TL;DR The tree command prints a directory and its contents as an