The standard way to get your running process’s PID in Go is through the os package: package main import ( “fmt” “os” ) func main() { pid := os.Getpid() fmt.Println(“Current PID:”, pid) } os.Getpid() returns an int representing the current process’s ID. This works across all platforms—Linux, macOS, Windows, and others. Getting the Parent Process…
Sometimes you need to find the ASCII character that comes after a given character. This is useful for generating sequences, creating substitution ciphers, or manipulating character ranges in shell scripts. Using printf with ASCII Values The most portable and straightforward approach uses printf to convert between characters and their ASCII numeric values: #!/bin/bash get_next_char() {…
The gethostname() function is the standard POSIX way to retrieve the system’s hostname. It’s straightforward to use and works across Unix-like systems. Basic Implementation #include <unistd.h> #include <stdio.h> int main() { char hostname[256]; if (gethostname(hostname, sizeof(hostname)) == 0) { printf(“Hostname: %s\n”, hostname); } else { perror(“gethostname”); return 1; } return 0; } The function takes…
Retrieving the hostname of the current system is a common task in systems programming, network applications, and monitoring tools. C++ provides several approaches depending on your platform and requirements. Using gethostname() The most portable approach uses the gethostname() function from <unistd.h>: #include <unistd.h> #include <iostream> #include <cstring> int main() { char hostname[256]; if (gethostname(hostname, sizeof(hostname))…
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 epoch timestamp (seconds since January 1, 1970 UTC) is fundamental for Unix timekeeping. Every process needs reliable time access — whether for logging, scheduling, or benchmarking. Basic Second-Level Precision For simple timestamp needs, use time(): #include <time.h> time_t now = time(NULL); printf(“Current epoch: %ld\n”, (long)now); This returns seconds since epoch as a time_t. It’s…
Epoch timestamps (seconds since January 1, 1970 UTC) are common in logs, databases, and APIs. Python’s datetime module handles conversion cleanly. Basic Conversion The simplest approach uses datetime.fromtimestamp(): from datetime import datetime epoch = 1609459200 dt = datetime.fromtimestamp(epoch) print(dt) # 2021-01-01 00:00:00 For UTC times specifically, use utcfromtimestamp(): from datetime import datetime, timezone epoch =…
Java provides multiple ways to get the current time as an epoch value. The right approach depends on whether you need milliseconds, seconds, or nanosecond precision, and whether you’re working with UTC or time zones. Using Instant for UTC timestamps The most straightforward method is Instant.now(): Instant now = Instant.now(); long epochSeconds = now.getEpochSecond(); long…
The epoch timestamp (also called Unix time) represents the number of seconds since January 1, 1970, 00:00:00 UTC. PHP provides several straightforward methods to obtain this value. Using time() The simplest approach is the time() function: <?php $timestamp = time(); echo $timestamp; // Output: 1704067200 (example) ?> This returns the current Unix timestamp as an…
The Unix epoch (seconds since January 1, 1970 UTC) is the standard for representing time across systems. Perl gives you straightforward access to this value. Basic epoch timestamp The simplest way to get the current epoch time: my $epoch = time(); print $epoch; # prints something like 1735689600 The time() function returns an integer representing…
Python offers several ways to get the current epoch timestamp, each suited to different use cases. The choice depends on your precision requirements and whether you’re working with timezone-aware operations. Using time.time() The simplest approach is time.time(), which returns the current time as a float representing seconds since the Unix epoch (January 1, 1970, 00:00:00…
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…
Processing files line by line is a common task in systems programming, data processing, and log analysis. C++ provides several approaches with different trade-offs in performance, memory usage, and code clarity. Using std::getline with std::ifstream The most straightforward approach uses std::getline with an input file stream: #include <fstream> #include <string> #include <iostream> int main() {…
Java has several solid REPL implementations available. Here are the main options and how to use them. jshell (Official) The best choice for most users is jshell, included in JDK 9+. It’s the official interactive shell for Java and comes with every modern Java installation. Start it immediately: jshell Basic usage: jshell> long ts =…
There are several ways to retrieve the hostname on a Linux system from Python. The choice depends on your use case and whether you need the simple hostname or the fully qualified domain name (FQDN). Using socket.gethostname() The simplest approach uses the socket module from the standard library: import socket hostname = socket.gethostname() print(hostname) This…
The most straightforward way to read an environment variable in Python is with os.getenv(): import os api_key = os.getenv(‘API_KEY’) print(api_key) If the variable doesn’t exist, getenv() returns None. You can provide a default value as a fallback: debug_mode = os.getenv(‘DEBUG’, ‘False’) port = os.getenv(‘PORT’, ‘8000’) For variables that must exist, use os.environ[] instead. This raises…
Disabling a user account is a common administrative task. Whether you’re offboarding an employee, removing an unused service account, or securing a compromised account, there are several approaches depending on your requirements. Lock the account with usermod The simplest method is to lock the password hash: sudo usermod -L username This prepends an exclamation mark…
Linux powers most of the cloud infrastructure, supercomputers, and embedded systems globally. The field itself spans kernel development, system administration, performance tuning, networking, and DevOps. Researching systems effectively requires understanding where to look, what tools matter, and how to validate your findings against real-world constraints. Start With the Right Foundation Before diving into specific research,…
When upgrading libvirt from an older version (like 1.2.2) to 2.5.0 or later, you may encounter a socket connection error when trying to create VMs: ERROR Failed to connect socket to ‘/var/run/libvirt/virtlogd-sock’: No such file or directory Domain installation does not appear to have been successful. This happens because libvirt 2.5.0 introduced the virtlogd daemon…
EncFS provides an encrypted filesystem in user space — files are encrypted on the fly and stored in an existing directory. It’s lighter than LUKS and doesn’t require root access or dedicated partitions. Here’s how to set it up on CentOS 6. Install EncFS EncFS is available from the EPEL repository: # Enable EPEL sudo…