You sometimes need to know whether your shell is running inside screen or tmux. The most straightforward approach is checking the TERM environment variable. Using TERM When screen starts a shell, it sets TERM=screen by default: [user@host ~]$ echo $TERM screen Compare this to a normal terminal session: [user@host ~]$ echo $TERM xterm-256color The TERM…
The basic syntax for setting an environment variable is: export VARIABLE=value No spaces around the equals sign. If your value contains spaces, quote it: export PATH_TO_PROJECT=”/home/user/my project” Verify it’s set: echo $VARIABLE Viewing all environment variables Use printenv to list all exported variables: printenv Or filter for a specific variable: printenv PATH The env command…
Use setenv to set an environment variable in csh: setenv VARIABLE value Replace VARIABLE with the name of the variable and value with its value. The variable is immediately available in the current shell and inherited by child processes. Examples Set a simple variable: setenv PATH /usr/local/bin:$PATH setenv EDITOR vim setenv JAVA_HOME /usr/lib/jvm/java-17-openjdk Use quotes…
Working with environment variables in C is straightforward using POSIX APIs. The two primary functions are getenv() for retrieval and setenv() for modification. Getting Environment Variables Use getenv() to read an environment variable: #include <stdlib.h> #include <stdio.h> int main(void) { const char *path = getenv(“PATH”); if (path != NULL) { printf(“PATH: %s\n”, path); } else…
When you need to page through error output from a command, you’ll run into the issue that less only receives stdout by default. Error messages go to stderr (file descriptor 2), so they’ll still scroll past on your terminal while stdout gets paged. Basic approach: combine stderr with stdout make 2>&1 | less The 2>&1…
There are several reliable methods to generate random strings of a specific length in bash. The choice depends on your character set requirements and use case. Using tr with /dev/urandom The tr command combined with /dev/urandom is the most portable and straightforward approach: tr -dc “[:alpha:]” < /dev/urandom | head -c 10 This produces a…
Cron is a minimal execution environment. Unlike your interactive shell, cron runs with a stripped-down environment containing only a few variables like PATH, MAILTO, and SHELL. Any variables you’ve defined in your shell profile won’t be available unless you explicitly source them in your crontab entries. The Problem If your cron job depends on environment…
SSH is essential for serious shared hosting management — it beats FTP by a mile and gives you real shell access for development, deployment, and automation. Most reputable shared hosting providers support SSH, though availability and implementation vary. Major Providers with SSH Support DreamHost DreamHost has long supported SSH on shared hosting. You’ll need to…
The –no-print-directory flag suppresses make’s default behavior of printing messages when entering and leaving subdirectories. If you invoke make frequently with recursive calls or have a deeply nested project structure, these messages clutter your output. Rather than passing the flag on every invocation, you can set it once in your Makefile. Add this line near…
Spawning background processes in Bash is straightforward with the & operator, but there are several nuances depending on your use case. Basic approach The simplest method is appending & to your command: for i in $(cat ./all-hosts); do ssh “$i” “ifconfig | grep Link” & done Each & launches the process in the background and…
When your distro’s package repositories lag behind, installing Scala directly from the official release is straightforward. This approach works on any Linux system with Java already installed. Prerequisites You’ll need a JDK installed. On most systems: # Debian/Ubuntu apt install default-jdk # RHEL/Fedora/CentOS dnf install java-17-openjdk-devel # Alpine apk add openjdk17 Verify your Java installation:…
You can run OCaml scripts directly from the command line with a shebang, similar to bash or Python. This requires making the file executable and using the proper interpreter directive. Basic Script Setup Create a file with a .ml extension and add a shebang at the top: #!/usr/bin/env ocaml print_endline “Hello world!”;; Then make 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…
GNOME can automatically restore your session—reopening all applications and windows that were running when you last logged out. This differs from autostart scripts, which launch specific programs on every login regardless of what was running before. Automatic Session Restoration To enable automatic session restoration in GNOME: Open Settings → General (or search “Session” in Activities)…
The default OCaml toplevel lacks basic readline features like history, line editing, and command completion. Here are the practical approaches to fix this. utop: Full-Featured Replacement The best option for daily interactive OCaml work is utop, a replacement toplevel that provides: Syntax highlighting with color output Command completion (for identifiers, keywords, library functions) Parenthesis and…
If you need to restart GNOME while keeping your applications open, you have several options depending on your GNOME version and setup. Quick restart with Alt+F2 The fastest method is to use GNOME’s run dialog: Press Alt + F2 Type r and press Enter This restarts the GNOME shell while preserving your running applications and…
Use usermod to add a user to supplementary groups. The -a (append) flag is critical — without it, you’ll remove the user from all groups not explicitly listed. usermod -a -G group_name user_name To add a user to multiple groups at once: usermod -a -G group1,group2,group3 user_name Options explained -a, –append Append the user to…
GNOME uses .desktop files in ~/.config/autostart/ to launch applications when you log in. This mechanism works across GNOME, XFCE, KDE, and most other modern desktop environments. Basic Setup Create a .desktop file in ~/.config/autostart/. Here’s a minimal example: [Desktop Entry] Type=Application Name=My Autostart Script Exec=/home/user/bin/myscript.sh Save this as ~/.config/autostart/myscript.desktop and it will run on your…
Pasting external code into Vim often triggers unwanted autoindent behavior, adding extra indentation and breaking formatting. Vim’s paste mode disables all automatic indentation while inserting text, letting you paste code exactly as-is. Quick paste mode toggle Enable paste mode before pasting: :set paste Then paste your code. When done, disable it: :set nopaste This works,…
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