Scripts sometimes need to run the same task with different input. A Bash function names a group of commands and accepts arguments when the script calls it. I’ll walk through passing arguments to functions and choosing between a status and printed data for results. TL;DR A Bash function gives a name to commands you can
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At the prompt, a script may receive a value typed by the user or capture output from a command. A shell variable gives that value a name the script can use later. In this piece, I’ll show how to assign and use Bash variables, including passing a value to a child process. TL;DR In Bash,
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Command output can fill a terminal, making its opening harder to inspect. The Linux head command prints the initial part of that output or a file. This article explains how to set line and byte counts, then combine head with tail to select a line range. TL;DR: Preview the beginning of a file Without a
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mv report.txt archive/ places report.txt inside the archive directory under its original name. I can’t resist the detail that a successful move removes the old source path rather than leaving a second copy. Follow the source operand to the destination operand to see where the file goes. Compare the paths to tell whether mv renames
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With mkdir -v -p project/src/assets, each created directory gets its own line. I love how that output makes each new level visible. Choose the directory path you want ready, either beneath your current directory or starting at the filesystem root. See what mkdir creates at that resolved location. What mkdir creates On a GNU Coreutils
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the current time the total uptime the number of active users and the average system loads for the past 1, 5 and 15 minutes. A one-minute load average higher than the longer-window averages means demand has risen recently. I can’t resist digging into how much that compact signal reveals about system activity without naming a
Uptime Command in Linux: Read the Output Read More »
With `sleep 30` running in the foreground, Ctrl+C can cut the wait short. I’m fascinated that a keypress can interrupt a running command without changing the rest of the computer’s power state. That matters when choosing between a timer and waiting for a child process to end. The command’s scope starts with the process `sleep`
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cat prints a file to your screen and stops there. The name is short for concatenate, because joining files is the job it was written for and reading a long one was never part of the plan. The cat command in Linux hands every byte of a file to standard output, so a long log
cat and more commands in Linux: Read, Join and Page Files Read More »
A for loop that renames files can act on half a filename, because bash splits the word list on whitespace before the body runs. A file holding the names report final.txt and notes.txt reaches the loop as three words, so the command in the body runs against a path that does not exist. Quoting inside
Bash for Loop in Shell Scripts: Syntax and Split Filenames Read More »
The while loop in shell script is the workhorse you reach for when you do not know how many iterations you need, so you must decide when to stop instead of how many times to run. I kept treating while test as boolean logic borrowed from Python, then hit silent failures around quoting, pipes, and
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