When you source a script using . script.sh or source script.sh, the $0 variable doesn’t point to the sourced script—it stays as the path of the parent shell or calling script. This creates a problem if you need the sourced script to know its own location. The solution: use ${BASH_SOURCE[0]} The ${BASH_SOURCE[0]} variable holds the…
If you need to jump to a particular byte position in a file, Vim provides the goto command. This is useful when debugging binary files, working with hex editors, or when error messages reference byte offsets. Using the goto command In normal mode, press go followed by the byte number: 20go This moves the cursor…
The tilde expansion ~username works fine when the username is literal, but fails when the username is stored in a variable like ~$user. Bash doesn’t perform tilde expansion on variables by default—it only expands ~ at the beginning of a word before variable expansion happens. Using eval The most common approach is to use eval:…
When you need to restrict a find-and-replace operation to a specific block of text, Vim gives you several approaches. Using the %V atom The most straightforward method is the %V atom, which restricts pattern matching to the current visual selection: :%s/%Vfrom/to/gc This works regardless of the visual mode you used (character, line, or block). The…
When renewing an SSL certificate, your CA will request a Certificate Signing Request (CSR). If you have the private key but need to generate a fresh CSR, OpenSSL handles this straightforwardly. Basic CSR Generation Generate a CSR from your existing private key: openssl req -new -key ssl.key -out req.pem This creates req.pem containing your CSR,…
To identify the developers who’ve contributed the most commits to a repository, use git log with some text processing: git log –format=’%aN’ | sort | uniq -c | sort -rn This returns a sorted list with commit counts and author names: 247 Paul Phillips 45 Dale Wijnand 12 Yamashita Yuu 10 Gilles Cornu 8 Josh…
Vim’s filetype detection usually works well, but sometimes it fails—especially with newly created files, unconventional extensions, or files without extensions. When that happens, you need to set the filetype manually. Setting Filetype in the Current Session The simplest way is to use the filetype option while Vim is open: :set filetype=php Replace php with whatever…
Backing up text messages from Android works best through Google Messages for real-time web access, or via ADB and third-party tools for local archives. Your approach depends on whether you need cloud sync, local storage, or both. Google Messages for Web (Easiest) The simplest method for most users is Google Messages, which syncs SMS and…
Getting the full or abbreviated commit hash is essential for scripting, CI/CD pipelines, and version tracking. Here are the standard approaches. Full commit SHA-1 To retrieve the complete commit hash of the current HEAD: git rev-parse HEAD This outputs the full 40-character SHA-1 hash. It works in any Git repository state and is reliable for…
Webpages often render differently when printed than on screen. Firefox’s developer tools make it straightforward to preview and debug print stylesheets without wasting paper. Using the CSS Media Type Emulator The fastest way to test print styles in Firefox: Open DevTools with F12 Click the Inspector tab (usually open by default) Look for the “Emulate…
Sorting text file lines by their length is useful for analyzing text patterns, finding anomalies, or preparing data for processing. Here are the most practical approaches. Using awk with sort The standard approach combines awk to calculate line length with sort to order them: awk ‘{ print length(), $0 | “sort -n” }’ /path/to/text/file This…
Bash provides several straightforward ways to test whether a string contains a substring. The best approach depends on your use case and performance requirements. Using [[ ]] with glob patterns The fastest and most Bash-native method is the [[ conditional construct with glob patterns: if [[ “$string” == *”substring”* ]]; then echo “Found it!” fi…
When accepting path input in Bash scripts, users might provide /path/to/dir/ or /path/to/dir. Normalizing these to a consistent format without the trailing slash is a common requirement. The Problem You need a reliable method that: Removes trailing slashes if present Works with both files and directories Handles paths that already lack a trailing slash Works…
Getting the directory path of a running script is a common requirement in bash, whether you’re sourcing files, building paths to config directories, or navigating relative to the script itself. The naive approach often fails with symbolic links or when the script is sourced rather than executed directly. The Problem Using $0 alone is unreliable….
By default, xargs appends its input as arguments at the end of the command. This works fine when you need a utility once per item, but becomes problematic when you need to reference the same input multiple times in different positions. The Problem Consider renaming files by appending .bak to each filename. You might try:…
When you run a command like this in Bash: ssh host1 hostname &; ssh host2 hostname & You get an error: bash: syntax error near unexpected token `;’ The issue stems from how Bash interprets command separators. The & and ; characters are both command terminators, but they serve different purposes, and Bash has strict…
When a process mmaps and mprotects many memory ranges, you’ll eventually hit the kernel limit and start seeing ENOMEM errors from mprotect() calls. This happens because Linux maintains internal kernel structures for each mapped range, and there’s a hard ceiling on how many the kernel will track per process. The culprit is the vm.max_map_count sysctl…
Writing a master thesis means protecting years of work. You need to handle three core concerns: preventing data loss from hardware failure or malware, ensuring 24/7 access to your work, and keeping it private until publication. The solution is version control with remote backup. Git provides local history and recovery, while a private remote repository…
The /etc/sysconfig/network-scripts/ directory contains network configuration files on RHEL and Fedora systems. While newer systems increasingly use NetworkManager and systemd-networkd, understanding ifcfg files remains essential for legacy systems and certain enterprise environments. Basic Static IP Configuration Here’s a typical ifcfg-eth0 file for a static IP setup: DEVICE=eth0 TYPE=Ethernet BOOTPROTO=none ONBOOT=yes IPADDR=192.168.1.151 NETMASK=255.255.0.0 GATEWAY=192.168.1.10 USERCTL=no The…
The free command—along with ps, top, kill, pgrep, and dozens of other system utilities—is maintained as part of the procps-ng project. Source repository The source code is hosted at: https://gitlab.com/procps-ng/procps You can clone it with: git clone https://gitlab.com/procps-ng/procps.git cd procps Most distributions package procps-ng, so you likely already have it installed. You can verify the…