When you open a new window with window.open(), you often need to communicate between the parent (opener) window and the child (opened) window. The most straightforward approach is to access the opener window directly through the opener property. Basic Two-Way Communication In the parent window, define a variable: let exchangeVar = ”; From the child…
When you open a popup window with window.open(), you’ll often need to detect when the user closes it so you can update your UI, refresh data, or clean up resources. Here are the practical approaches, from polling to event-driven methods. Polling the closed property The simplest method is to periodically check the popup’s closed property:…
Automating keyboard input on Linux is useful for testing, accessibility workflows, and automation scripts. If you need to simulate pressing multiple keys simultaneously and holding them, xdotool is the standard tool for this job. Basic approach with xdotool The keydown and keyup commands let you press and release individual keys without triggering the other. To…
When you’re processing text with varying amounts of whitespace between fields, the standard cut command falls short. Given input like this: a b c d You need a way to reliably extract fields regardless of how many spaces separate them. Here are the practical approaches. Using tr with cut The tr command can normalize whitespace…
Getting a file’s size is a common task in Python. There are several ways to do it, depending on what you need and how much detail you want about the file. Using os.path.getsize() The simplest approach is os.path.getsize(): import os file_path = ‘/path/to/your/file.txt’ size_bytes = os.path.getsize(file_path) print(f”File size: {size_bytes} bytes”) This returns the size in…
When you need to traverse a directory tree in Python, you have several options. The choice depends on whether you want recursive traversal, how you want to handle the results, and your Python version. Using os.walk() The os.walk() function is the classic approach for recursively iterating through directories. It yields tuples of (dirpath, dirnames, filenames)…
The most reliable way to get a file extension in Python is os.path.splitext(), which splits a filename into the base name and extension. For modern code, pathlib.Path provides a cleaner alternative. Using os.path.splitext() os.path.splitext() returns a tuple of (name, extension): import os name, ext = os.path.splitext(‘file.txt’) print(name) # ‘file’ print(ext) # ‘.txt’ This works with…
The git status command shows repository state visually, but when you need to detect it programmatically in bash — say, to fail a CI pipeline or prevent deployments — you need a different approach. Quick Method: Check Unstaged Changes The most reliable way to detect uncommitted changes is with git diff: if [[ -n $(git…
When working with file I/O in C on Linux, you’ll often need to convert between low-level file descriptors (returned by open(), socket(), etc.) and higher-level FILE pointers (returned by fopen()). This is common when integrating different libraries or mixing POSIX I/O with standard C I/O. Getting a FILE Pointer from a File Descriptor Use fdopen()…
When troubleshooting email delivery or verifying mail server configuration, you need to look up the MX (Mail Exchange) records for a domain. On Linux, two tools handle this: host and dig. Both are reliable, though dig is generally preferred for its flexibility and cleaner output format. Using dig to query MX records The dig command…
When you need writes to one or more files to automatically go to another file, you have several options depending on your exact use case. The most common scenario is capturing output from commands, monitoring file changes, or duplicating writes across multiple destinations. Using tee for Command Output Duplication The tee command duplicates standard input…
When working with text files containing long lines, you often need to reformat them to fit within a specific column width—typically 80 characters for readability or compatibility. Linux provides several utilities to handle this, with fold being the most straightforward option. Using fold The fold command breaks lines to fit a specified width without requiring…
Skype periodically fails to start with a “system is unavailable” error when it can’t read or write to the user’s temporary directory. This typically happens when the temp folder becomes corrupted, has permission issues, or contains orphaned Skype cache files that prevent proper initialization. Understand the Problem On Windows, each user account has a temporary…
By default, Fedora doesn’t enable SSH access. You’ll need to install OpenSSH server, start the service, and configure your firewall to allow connections. Install OpenSSH Server sudo dnf install openssh-server openssh-clients Start and Enable the SSH Service sudo systemctl start sshd sudo systemctl enable sshd The enable flag ensures sshd starts automatically on boot. Verify…
When you have multiple static libraries (.a files) and need to combine them into a single archive, GNU ar provides several approaches. The most straightforward method uses ar‘s MRI mode for clarity and maintainability. Using ar MRI Mode The cleanest approach is to use ar -M with an MRI script. This method is explicit and…
Fedora uses systemd-tmpfiles to automatically clean up temporary files and directories. By default, this includes volatile files in /tmp/, which can cause problems for applications that rely on files persisting there — like HDFS DataNodes that store their PID files as hadoop-hadoop-datanode.pid. How systemd-tmpfiles Works The systemd-tmpfiles service runs periodically (typically daily and at boot)…
Vim supports Xterm 256-color codes on Linux and modern terminals. Understanding the color palette and how to use it in your configuration is essential for building readable syntax highlighting schemes and custom colorschemes. The 256-Color Palette Xterm’s 256-color mode consists of: Colors 0-15: Standard ANSI colors (black, red, green, yellow, blue, magenta, cyan, white, and…
These kernel messages from the libata driver indicate SATA link-layer errors between your drive and controller. They look alarming, but they’re usually fixable — and the fix is typically hardware-related, not a software or drive firmware issue. What These Error Messages Mean When you see messages like this in dmesg: ata4.00: exception Emask 0x10 SAct…
When you run a curl GET request with spaces in the query string, the shell interprets the space as a separator and truncates the URL: curl “http://example.com/send?msg=hello world” The space causes the shell to treat world as a separate argument, so only hello gets sent. You need to properly URL-encode the space (and other special…
When sending POST requests through a Squid proxy with curl, you may encounter a proxy error that blocks the request, even though the same request works fine with GET. The issue typically appears as: ERROR The requested URL could not be retrieved The root cause is the Expect: 100-continue header that curl automatically adds to…