These four languages share functional programming roots but diverge significantly in syntax and design philosophy. Here’s a practical reference for anyone transitioning between them or evaluating which to use. Basic Function Definition OCaml: let add x y = x + y let rec factorial n = if n <= 1 then 1 else n *…
Running your own Python installation on Dreamhost (or similar shared hosting) gives you control over the version, packages, and dependencies without relying on system-wide Python. This is especially useful when you need specific Python versions or packages the hosting provider doesn’t support. Why Use a Custom Python Installation Shared hosting environments typically ship with outdated…
Linux systems can have multiple timer sources available, and the kernel selects one as the active clocksource. Understanding what’s available and how to view or change the current source is essential for performance tuning and troubleshooting timing-related issues. View the Current Timer Source Check which clocksource is currently in use: cat /sys/devices/system/clocksource/clocksource0/current_clocksource This will output…
You have an LVM physical volume (PV) you need to remove from a volume group (VG), but the data needs to be preserved and moved to other available PVs. This is a straightforward but important operation that requires careful execution. Prerequisites Before starting, verify: The VG has sufficient free space on remaining PVs to accommodate…
When you need to execute a system command and capture its output in C, popen() is the standard approach. Unlike system(), which just runs a command, popen() gives you a file stream connected to the command’s stdout or stdin. Basic Usage The popen() function signature is: FILE *popen(const char *command, const char *type); The type…
The Unix epoch (January 1, 1970 00:00:00 UTC) is the standard reference point for timestamps across Linux systems. When you need to convert a timestamp like 1349361711.169942 into a readable date, the date command is your primary tool. Basic Conversion The simplest approach uses date with the @ prefix: date -d @1349361711.169942 Output: Thu Oct…
Counting page views isn’t as simple as incrementing a counter. You need to handle edge cases: duplicate views from the same user, multiple users behind a single IP (corporate networks), and bots. Here’s how to build a robust system. The Problem with IP-Based Counting Relying on IP addresses fails in several scenarios: Multiple users behind…
Start by compiling your C source files into object files: gcc -c lib1.c lib2.c This produces lib1.o and lib2.o. You can use any compiler flags here—-Wall, -O2, -fPIC, etc.—that match your build requirements. Position-independent code (-fPIC) isn’t strictly required for static libraries but is good practice if you anticipate reusing these objects elsewhere. Creating the…
Setting environment variables in Bash is one of the most fundamental skills for working with Linux command lines and shell scripts. Bash provides several ways to define and manage variables. Setting a Variable for the Current Shell MY_VAR=”hello world” Important: No spaces around the = sign. MY_VAR = “value” will produce an error because Bash…
Accessing Linux filesystems from Windows is useful when dual-booting, migrating data, or recovering files. Read-only access is essential to prevent accidental corruption of ext4 metadata and data. Why Read-Only Access Matters Ext4 is designed for Linux environments. Windows drivers lack complete understanding of ext4 journaling, extended attributes, and other advanced features. Writing through an incomplete…
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…
PuTTY stores session configurations in the Windows Registry. If you’re migrating to a new computer, setting up multiple workstations, or just want a backup, here’s how to export and backup your PuTTY sessions. Export from Windows Registry PuTTY sessions are stored at HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\Sessions. Export them using regedit or the command line: # Export all PuTTY…
MySQL replication lets you maintain synchronized copies of your database across multiple servers. This is essential for high availability, read scaling, and backups. Here’s how to configure it properly. Prerequisites You need at least two MySQL instances: a primary (source) and one or more replicas. Both should run the same or compatible MySQL versions. MySQL…
If you’re trying to add a domain to a Dreamhost account and get the error “You can’t add that domain: already in our system,” the domain is already configured for DNS hosting in another Dreamhost account. You need to remove the DNS hosting from the original account before you can host it elsewhere. This process…
The OCaml compiler only finds the standard library (List, Array, etc.) by default. Third-party libraries require you to explicitly tell the compiler where to find them. Using ocamlfind The standard approach is ocamlfind, a package manager that tracks installed libraries and their locations. It’s part of the OPAM ecosystem and should already be installed if…
The maximum array length in OCaml is platform-dependent and can be queried at runtime using Sys.max_array_length: # Sys.max_array_length;; – : int = 4611686018427387903 Values by Platform 64-bit systems: # Sys.max_array_length;; – : int = 4611686018427387903 32-bit systems: # Sys.max_array_length;; – : int = 1073741823 Note that 32-bit OCaml support has been deprecated in recent versions….
Determining the number of CPU cores available on a Linux system is essential for performance tuning, application configuration, and capacity planning. Several approaches exist depending on what information you need. Quick check: nproc The simplest way to get the number of CPU cores is nproc: $ nproc 8 This reports the number of logical processors…
To check which storage engine a table uses, query the information_schema database: SELECT ENGINE FROM information_schema.TABLES WHERE TABLE_SCHEMA = ‘database_name’ AND TABLE_NAME = ‘table_name’; Replace database_name and table_name with your actual values. You can also use the SHOW TABLE STATUS command for a quicker view: SHOW TABLE STATUS FROM database_name WHERE Name = ‘table_name’\G The…
If gnuplot or ps2epsi fails to run or produces excessive warnings on modern Fedora systems, you’re likely hitting a fontconfig deprecation issue. The symptom is repeated warnings like: Fontconfig warning: “/etc/fonts/conf.d/50-user.conf”, line 14: reading configurations from ~/.fonts.conf is deprecated. This happens because /etc/fonts/conf.d/50-user.conf still includes a deprecated reference to ~/.fonts.conf. While the warning alone doesn’t…
Handling Ctrl-C gracefully in a Bash script is essential when you need to perform cleanup operations, save state, or notify users before exiting. The trap builtin makes this straightforward. Basic Trap Setup The fundamental approach uses the trap command to catch the INT signal (which Ctrl-C generates): trap ctrl_c INT function ctrl_c() { echo “Ctrl-C…