Printing Fields After a Specific Field in awk
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Adding a Prefix to Each Line in Bash
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Detecting File Writes by Other Processes in Linux
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Querying Maximum Temperature Across Linux Server Sensors
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Counting reads per chromosome in BAM files
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Splitting a gzip file into smaller files on Linux
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Terminating a Bash Script and Its Child Processes in Linux
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Getting File Modification Time on Linux
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Printing to STDERR and STDOUT in OCaml
In OCaml, the standard library provides straightforward functions for writing to standard output and standard error. Printing to STDOUT Use print_endline to write a string followed by a newline to standard output: print_endline “hello world!” This function is in the Stdlib module (formerly Pervasives in older OCaml versions) and automatically flushes the output buffer. The…
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Printing to STDERR and STDOUT in C++
In C++, you have several ways to output to standard output and standard error streams. The choice depends on your project’s requirements and whether you’re working with older codebases or modern C++. Using std::cout and std::cerr The standard approach uses the C++ iostream library: #include <iostream> int main() { std::cout << “This goes to standard…
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Printing to STDERR and STDOUT in C
The fundamental distinction between standard output and standard error matters for proper program behavior, logging, and stream redirection. Here’s how to handle both correctly. Basic Approach with fprintf() The simplest method uses fprintf() to write to specific streams: #include <stdio.h> int main() { fprintf(stdout, “This goes to standard output\n”); fprintf(stderr, “This goes to standard error\n”);…
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How to Write Output to STDERR and STDOUT in PHP
In PHP, STDOUT and STDERR are standard output streams that handle different types of output. STDOUT carries normal program output, while STDERR carries error messages and diagnostic information. Properly directing output to the correct stream is essential for building reliable scripts and applications. Using fwrite() with Stream Handles The most straightforward approach uses fwrite() with…
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Printing to STDERR and STDOUT in Bash
Understanding file descriptors is fundamental to shell scripting. By default, your shell has three standard streams: STDOUT (FD 1): Standard output, where commands print results STDERR (FD 2): Standard error, where commands print errors and diagnostics STDIN (FD 0): Standard input, where commands read data Basic Output Print to STDOUT: echo “This goes to stdout”…
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Printing to stderr and stdout in Go
Go provides straightforward ways to write to standard output and standard error streams. Understanding when and how to use each is essential for building robust applications, especially in containerized and cloud environments where log separation matters. Using the fmt Package The fmt package is the most common approach for printing to STDOUT: package main import…
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How to Get a Process’s Parent ID in Python
To get the parent process ID (PPID) of the running process, use the os.getppid() function: import os ppid = os.getppid() print(f”Parent Process ID: {ppid}”) This returns the process ID of the parent process as an integer. On Unix-like systems, this is straightforward. On Windows, the behavior is consistent as well. Accessing Full Process Information For…
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How to Get a Process’s Parent PID in C/C++
To retrieve the parent process ID (PPID) of the current running process, use the getppid() system call. This is the standard and portable approach on Unix-like systems including Linux. #include <stdio.h> #include <unistd.h> int main() { pid_t ppid = getppid(); printf(“Parent process ID: %d\n”, ppid); return 0; } Compile and run: gcc -o get_ppid get_ppid.c…
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How to Get a Process’s Parent ID in Bash
Every process running on a Unix-like system has a parent process. The parent process ID (PPID) identifies which process spawned the current one — critical information when debugging process hierarchies, managing child processes, or writing robust shell scripts. Built-in variable The simplest approach uses Bash’s $PPID variable: echo $PPID This prints the PPID of the…
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Debugging Bash Scripts: Essential Techniques
Bash has several native flags that help you trace and validate script execution before and during runtime. Trace mode (-x): Executes the script while printing each command before it runs. bash -x script.sh This prints expanded commands to stderr, showing variable substitution and command execution order. You can enable tracing for specific sections using set…
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Getting a Process PID in Bash
Every shell script runs as a process with a unique ID (PID). You need this ID for process management, logging, temporary file naming, and cleanup operations. The $$ variable The special variable $$ expands to the PID of the current shell process: echo $$ This returns a single integer — the PID of your current…
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Finding the Root Filesystem Disk in Linux Bash
On Linux systems, the root filesystem (/) can be on various device types — a raw disk partition, an LVM logical volume, or other storage configurations. Finding the underlying physical disk requires checking the device hierarchy, which differs depending on the storage setup. Quick method with df and lsblk The simplest approach uses lsblk with…