Several methods exist to prepend a prefix string to each line of text. The right approach depends on your input source and performance requirements. Using sed The sed stream editor is the most portable and efficient approach: sed ‘s/^/PREFIX/’ file.txt This uses a substitution command where ^ matches the start of each line and PREFIX…
Monitoring server temperatures is essential for preventing hardware damage and maintaining system stability. Linux provides several tools to query thermal sensors and identify which components are running hot. Using lm-sensors The most reliable approach is lm-sensors, a userspace tool that reads temperature data from kernel drivers: # Install lm-sensors sudo apt install lm-sensors # Debian/Ubuntu…
When you need to break up a large gzip file into smaller chunks, you have several practical options depending on your constraints. Using zcat with split The most straightforward approach is to decompress the gzip file and split it simultaneously: zcat large_file.gz | split -b 100M – chunk_ gzip chunk_* This decompresses large_file.gz, pipes it…
When a Bash script spawns child processes—say script A starts B, which starts C, which runs rsync—you need a way to terminate the entire process tree cleanly. Simply killing the parent leaves orphaned children running in the background. The most reliable approach uses session IDs (SID). By default, child processes inherit the same session ID…
Google Maps integration is straightforward, but the approach depends on whether you need an interactive map or a static image. Each has trade-offs worth understanding. Static Map Images For a simple, lightweight solution, use Google’s Static Maps API. This generates a single PNG image without requiring JavaScript or API interactions. <img src=”https://maps.googleapis.com/maps/api/staticmap?center=40.714728,-73.998672&zoom=12&size=600×400&key=YOUR_API_KEY” alt=”Map of New…
Perl gives you straightforward ways to send output to both standard output and standard error. Understanding the difference matters — STDOUT handles normal program output, while STDERR carries diagnostics, warnings, and error messages. Separating them lets users redirect, log, or suppress errors independently. Basic Output Methods The simplest approach uses print with filehandles: print STDOUT…
In PHP, STDOUT and STDERR are standard output streams that handle different types of output. STDOUT carries normal program output, while STDERR carries error messages and diagnostic information. Properly directing output to the correct stream is essential for building reliable scripts and applications. Using fwrite() with Stream Handles The most straightforward approach uses fwrite() with…
Understanding file descriptors is fundamental to shell scripting. By default, your shell has three standard streams: STDOUT (FD 1): Standard output, where commands print results STDERR (FD 2): Standard error, where commands print errors and diagnostics STDIN (FD 0): Standard input, where commands read data Basic Output Print to STDOUT: echo “This goes to stdout”…
By default, print() writes to STDOUT. Both STDOUT and STDERR go to your terminal unless you redirect them. Here’s how to send output to each stream explicitly. Printing to STDOUT The standard print() function writes to STDOUT and automatically adds a newline: print(“your message”) Printing to STDERR To print to STDERR, pass the file parameter:…
Every process running on a Unix-like system has a parent process. The parent process ID (PPID) identifies which process spawned the current one — critical information when debugging process hierarchies, managing child processes, or writing robust shell scripts. Built-in variable The simplest approach uses Bash’s $PPID variable: echo $PPID This prints the PPID of the…
Bash has several native flags that help you trace and validate script execution before and during runtime. Trace mode (-x): Executes the script while printing each command before it runs. bash -x script.sh This prints expanded commands to stderr, showing variable substitution and command execution order. You can enable tracing for specific sections using set…
Every shell script runs as a process with a unique ID (PID). You need this ID for process management, logging, temporary file naming, and cleanup operations. The $$ variable The special variable $$ expands to the PID of the current shell process: echo $$ This returns a single integer — the PID of your current…
On Linux systems, the root filesystem (/) can be on various device types — a raw disk partition, an LVM logical volume, or other storage configurations. Finding the underlying physical disk requires checking the device hierarchy, which differs depending on the storage setup. Quick method with df and lsblk The simplest approach uses lsblk with…
Extracting or removing trailing numbers from strings is a common task in shell scripting. Whether you’re parsing log files, processing configuration values, or cleaning up filenames, you’ll need reliable methods to handle these operations. Using Parameter Expansion The cleanest approach uses bash parameter expansion, which doesn’t require external commands and works in all POSIX-compliant shells….
Retrieving the hostname of the machine running your script is essential for logging, node identification in distributed systems, monitoring, and conditional logic based on where code executes. Bash offers multiple approaches with different tradeoffs. Using the $HOSTNAME Variable The quickest method is the $HOSTNAME environment variable, which Bash sets at shell initialization: echo $HOSTNAME host01…
The date command is your primary tool for retrieving Unix epoch timestamps. It’s available on virtually all Unix-like systems and integrates seamlessly into scripts and command pipelines. Basic Epoch Timestamp date +%s This returns the number of seconds since January 1, 1970 UTC. Output looks like 1735689600. Higher Precision with Nanoseconds For microsecond or nanosecond…
Environment variables store configuration settings for your shell and applications. They’re essential for configuring containers, serverless functions, application runtime behavior, and system services. Retrieving an environment variable Use the dollar sign prefix to access a variable: echo $VARIABLE_NAME This prints the variable’s value to stdout. If the variable doesn’t exist, it prints an empty line….
Bash provides several methods to process files line by line, each with different performance characteristics and use cases. Using a While Loop with IFS The most common approach uses a while loop with the read builtin: while IFS= read -r line; do echo “Processing: $line” done < filename.txt Breaking this down: IFS= prevents leading/trailing whitespace…
Go compiles quickly and go run handles small scripts, but a REPL is more practical for interactive testing and exploration. Here are the best options available today. gore gore remains the most mature Go REPL. It’s actively maintained and handles most interactive development workflows. Install it: go install github.com/motemen/gore/cmd/gore@latest Basic usage: $ gore gore version…
Process priority management is essential for ensuring critical tasks get CPU resources when needed. Linux provides several mechanisms to control how the kernel scheduler allocates CPU time to processes. Understanding Priority Levels Linux uses two priority concepts: Nice value: ranges from -20 (highest priority) to 19 (lowest priority). Default is 0. Real-time priority: ranges from…