Shell scripting (Bash, awk, sed), Unix utilities, file handling, string manipulation, and command-line tools.
The most reliable one-liner to count files in the current directory is: find . -maxdepth 1 -type f | wc -l This counts only regular files (not directories or symlinks) and handles edge cases that trip up simpler approaches. Why Not Use ls | wc -l? The common ls | wc -l command has several…
Parsing directory and filename components from an absolute path is a common task in systems programming. Linux provides dirname() and basename() functions for this purpose, but they have implementation-specific behaviors that can cause bugs if you’re not careful. Using dirname() and basename() The POSIX standard defines both functions, though the implementations vary. Here’s the safest…
The nl command is purpose-built for adding line numbers to text files: nl text-file By default, nl numbers all non-empty lines and skips blank lines. This behavior is controlled by the body section style, which defaults to t (text only). Common nl options Number all lines including blanks: nl -ba text-file Start numbering at a…
You have internal hosts on a private network (like 10.0.3.0/24) that aren’t directly accessible from your workstation. They sit behind a gateway (bastion host) like gateway.example.org. You need seamless SSH access to these internal IPs without manually hopping through the gateway each time. Using SSH ProxyJump The modern, straightforward approach is SSH’s built-in ProxyJump feature….
When you have shared Makefiles included across multiple projects in different directory structures, relative includes break. If common.mk tries to include release.mk and both files are in a subdirectory like external/, the include fails because Make uses the current working directory, not the location of the including file. For example, this structure works fine: Makefile…
GNOME Shell’s appearance, including the panel, notifications, and system UI, is controlled by CSS theme files. Font customization requires editing these theme files directly. System-Wide Font Changes The primary theme file for GNOME Shell is located at: /usr/share/gnome-shell/theme/gnome-shell.css To modify fonts, open this file with elevated privileges: sudo nano /usr/share/gnome-shell/theme/gnome-shell.css Search for font-family declarations throughout…
By default, WordPress contributors can submit and edit their own posts, but they can’t upload media files. If you want contributors to attach images or documents to their submissions, you’ll need to grant them the upload capability. Method 1: Using User Role Editor Plugin The User Role Editor plugin is the most straightforward approach for…
Gnuplot can output directly to EPS (Encapsulated PostScript) format, which is useful for including plots in LaTeX documents and other publishing workflows. Direct EPS Output The simplest approach is to set the terminal to postscript with the eps option before plotting: set terminal postscript eps enhanced mono “Helvetica” 14 set output “my-plot.eps” plot sin(x) This…
When you need to rsync against hosts behind NAT gateways or port-forwarded SSH services, the standard port 22 won’t work. The solution is the -e flag, which lets you specify a custom SSH command with your desired port. Basic usage Use -e to pass custom SSH arguments: rsync -avxP –delete -e “ssh -p 13022” username@example.com:/remote/path/…
You’ve accidentally broken a file and need to restore it from an earlier commit without touching anything else in your repository. Here’s how. Restore a file to a specific commit To restore my_file.name to its state at a specific commit: git checkout commit_sha1 my_file.name Replace commit_sha1 with the actual commit hash. You can find it…
Managing OCaml packages effectively depends on your workflow and environment. The current standard is OPAM (OCaml Package Manager), which handles dependency resolution, version switching, and sandboxed environments. OPAM: The Standard Choice OPAM is the de facto package manager for OCaml and is maintained by the OCaml community. Install it using your system package manager or…
Converting strings to long integers is fundamental in C. The standard library provides strtol(), strtoul(), strtoll(), and strtoull() for this purpose. These functions handle the conversion robustly and let you detect parsing errors through their return value and endptr argument. Function Signatures All four functions share a similar interface: long strtol(const char *str, char **endptr,…
When managing many systems, manually confirming host keys for each new connection gets tedious fast. You can configure SSH to automatically add unknown hosts to ~/.ssh/known_hosts without prompting. The Risk Trade-off Before implementing this, understand what you’re doing: disabling strict host key checking opens you to man-in-the-middle attacks. Only use this in trusted networks where…
When passwordless SSH authentication fails despite proper key setup, start by checking the SSH daemon logs to identify the actual problem. Checking SSH Logs The SSH daemon logs are your primary diagnostic tool: sudo tail -f /var/log/auth.log # Debian/Ubuntu sudo tail -f /var/log/secure # RHEL/CentOS/Fedora sudo journalctl -u ssh -f # systemd-based systems Watch the…
X11 forwarding over SSH lets you run graphical applications on remote systems and display them locally. Firefox is a common use case, though it requires careful configuration to avoid crashes and permission issues. Basic Setup The simplest approach uses X11 forwarding: ssh -X remotehost The -X flag enables trusted X11 forwarding. For untrusted forwarding (more…
To convert a PostScript file to PDF suitable for publishing, use ps2pdf from the Ghostscript suite: ps2pdf -dPDFSETTINGS=/printer file.ps file.pdf The /printer setting produces high-quality output appropriate for publication. Other available quality settings include: /screen — lowest quality, smallest file size /ebook — medium quality, reasonable file size /printer — high quality, suitable for printing…
If you’re working on Windows but need to interact with Linux systems, you’ll need reliable remote access tools. SSH is the standard—it’s secure, scriptable, and works everywhere. Here’s what actually matters. SSH Clients Windows Terminal + OpenSSH is the baseline for Windows 11. It’s built-in, integrates native SSH without extra installation, and handles key authentication…
GNOME Shell’s clean, minimal design works well for many users, but the extension ecosystem lets you adapt it to your actual workflow. Here are extensions worth considering for modern GNOME (45+). AlternateTab Changes Alt-Tab behavior from application-grouped switching to per-window switching — more like traditional window managers. If GNOME’s default grouping feels disruptive, this restores…
When a Bash script needs to reference its own location — for sourcing additional files, logging, or managing relative paths — $0 seems like the obvious choice. But it’s a trap: $0 behaves differently depending on whether your script is executed directly or sourced. The Problem with $0 When you execute a script directly: ./script.sh…
SSH tunneling on Windows routes your traffic through a remote server over an encrypted connection, letting you bypass network restrictions and access resources as if you were on the remote network. The setup creates a SOCKS proxy that listens locally and forwards all traffic through the SSH tunnel. The traffic flow is straightforward: Your application…