![What is the difference between [ ] and [[ ]] for conditional tests?](https://img.php.cn/upload/article/001/253/068/175147485122458.jpg?x-oss-process=image/resize,m_fill,h_135,w_240)
What is the difference between [ ] and [[ ]] for conditional tests?
In Bash scripts, [] is synonymous with the test command, suitable for portability across shells; [[]] is the Bash keyword, providing more powerful and secure features. 1.[] variables need to be strictly referenced to avoid errors, while [[]] is more tolerant to unreferenced variables; 2.[[]] supports regular expression matching (=~) and wildcard pattern matching (==), while [] does not support it; 3.[[]] allows the use of && and || combination conditions without additional brackets; 4. If cross-platform compatibility is required, [] should be used. If it is for Bash, it is recommended to use [[]] for clearer syntax and advanced features.
Jul 03, 2025 am 12:47 AM
How to make the taskbar transparent in Windows 10?
The taskbar transparency can be achieved in three ways on Windows 10. 1. Enable the "Transparent Effect" that comes with the system: Check "Make the Start Menu, Taskbar and Operation Center transparent" in "Settings>Personalization>Color" to obtain a hazy effect; 2. Adjust the transparency through the registry editor: Modify the EnableBlurBehind and DwmSystemBackdropType values ??to enable the Mica effect, and restart the Explorer or the computer to take effect; 3. Use third-party tools such as TranslucentTB, Rainmeter or WindowBlinds to achieve a more thorough transparent effect, but pay attention to the download source and compatibility issues.
Jul 03, 2025 am 12:47 AM
How to mount an ISO file in Windows?
The ISO file mount of Windows system can be directly completed through the system's own functions. First, double-click the ISO file to automatically mount it, and the system will assign it an independent optical drive letter; secondly, right-click the ISO file and select "mount" to achieve the same effect, suitable for users who need precise operation; in addition, the system supports mounting multiple ISO files at the same time, each of which is displayed as an independent optical drive. When uninstalling, just right-click the corresponding optical drive and select "Eject" to it, but be careful that the mount content will not be retained after restarting.
Jul 03, 2025 am 12:45 AM
Why is my Windows 10 camera not working?
When the camera cannot be used, first confirm whether it is occupied by other programs, then check the permission settings, then update or reinstall the driver, and finally run the system troubleshooting tool. 1. Close the program that occupies the camera and restart the computer; 2. Enter the privacy settings to enable camera permissions and specific application permissions; 3. Update or uninstall the camera driver through the device manager to restart the system to automatically install it; 4. Use the "Windows Camera" tool in "Troubleshooting" to detect problems. Most of the cases are software or permission problems, and there is no need to replace the hardware.
Jul 03, 2025 am 12:45 AM
What to do when Windows 10 is stuck on the loading screen?
When Windows 10 is stuck in the loading interface, you can try the following methods to solve it: 1. Disconnect all non-essential external devices and check whether the memory and hard disk cable are plugged in; 2. Force shutdown more than twice to enter the recovery environment, use "Start Repair" or command prompt to execute bcdedit/settestsigningoff; 3. Rewind to the previous normal state through the system restore point; 4. Use the installation USB flash drive to run the bootrec/fixmb, bootrec/fixboot, bootrec/rebuildbcd commands to repair the system; if it still cannot be solved, consider backing up the data and reinstalling the system.
Jul 03, 2025 am 12:43 AM
What is the Linux terminal and how do I use it?
TheLinuxterminalisapowerfultext-basedinterfacethatallowsuserstointeractwiththesystemthroughcommands.1.Itprovidesaccesstotheshell,enablinguserstorunsystemcommandslikels,cd,cp,andrm.2.Itisusedforinstallingandmanagingsoftwarepackages.3.Ithelpsinviewingl
Jul 03, 2025 am 12:41 AM
Windows blue screen on startup
The computer boots up the blue screen is usually caused by driver conflicts, hardware failures or system files corruption. The solutions are as follows: 1. Check the newly installed hardware or updated driver, unplug the external device or uninstall the latest driver; 2. Enter safe mode to uninstall the software, restore the system or detect viruses; 3. Troubleshoot overclocking problems through factory reset of BIOS; 4. Use the installation USB drive to repair the system files or check the bad hard disk; 5. If it cannot be solved, try reinstalling the system or detecting hardware failures.
Jul 03, 2025 am 12:38 AM
How to factory reset Windows 10?
The ways to reset Windows 10 include backing up files, accessing reset options in settings, selecting the appropriate reset method and letting it complete. First, back up important data to an external hard disk or cloud storage; then go to "Settings>Update and Security>Recover", click "Reset this computer" and select "Delete all contents"; then select "Cloud Download" or "Local Reinstall" according to the situation; finally make sure the device is powered on and complete the reset process, without interruption during this period.
Jul 03, 2025 am 12:34 AM
How to create a self-signed SSL certificate using OpenSSL?
The key steps for creating a self-signed SSL certificate are as follows: 1. Generate the private key, use the command opensslgenrsa-outselfsigned.key2048 to generate a 2048-bit RSA private key file, optional parameter -aes256 to achieve password protection; 2. Create a certificate request (CSR), run opensslreq-new-keyselfsigned.key-outselfsigned.csr and fill in the relevant information, especially the "CommonName" field; 3. Generate the certificate by self-signed, and use opensslx509-req-days365-inselfsigned.csr-signk
Jul 03, 2025 am 12:30 AM
What is DevOps and what are its core principles (CAMS)?
DevOpsisaculturalandprofessionalmovementthatbridgessoftwaredevelopmentandIToperationsthroughcollaboration,automation,andcontinuousimprovement.1.Culturefostersteamworkandsharedresponsibilitybybreakingdownsilos.2.Automationstreamlinestasksliketesting,d
Jul 03, 2025 am 12:23 AM
How to exit Vim in Linux
To exit Vim, you must first press the Esc key to enter command mode, then enter: q and press Enter to exit. If the file has been modified and wants to save and exit, use:wq to enter; if you do not want to save and force exit, use:q! to enter. Reasons for not being able to exit may include not entering command mode correctly, files being locked or read-only, spelling errors, and files being occupied by other programs. The solutions are to ensure that Esc is pressed to enter command mode, use q! to exit and abandon changes, check the spelling of the command, and close the program that occupies the file. Additionally, you can use nano instead of Vim or configure the default editor to nano to simplify operations. Mastering these basic steps is one of the keys to Linux operations.
Jul 03, 2025 am 12:21 AM
How to dual boot Linux and Windows
The key to installing a dual system is partitioning and boot settings. Just pay attention to the following points to run stably: ① Back up data before partitioning, use Windows disk management or third-party tools to make unallocated space available. Linux is recommended to separate /, /home and swap separately; ② The installation order must be Windows after Linux, otherwise the boot needs to be repaired manually; ③ Make sure that the boot mode of UEFI or Legacy is consistent, and select the right boot position during installation such as /dev/sda; ④ The boot menu can be adjusted through grub-customizer or editing grub files, and enter Linux after a few seconds by default. Be sure to carefully confirm each step during operation to avoid problems caused by misoperation.
Jul 03, 2025 am 12:18 AM
What is Linux?
Linux is an open source operating system kernel and has now developed into a variety of distributions such as Ubuntu, Debian, and CentOS. 1. The kernel is the core of the system, managing hardware resources and providing an operating environment; 2. Linux is open source free, Windows/macOS closed source commercial; 3. Linux users are mostly developers and advanced users, stable and secure, suitable for servers; 4. High degree of freedom, good performance, strong community support, suitable for development and learning; 5. It can be tried through virtual machines, beginner distributions, and LiveCD modes.
Jul 03, 2025 am 12:16 AM
How to find my Windows product key?
TofindyourWindowsproductkey,youcanchecktheregistryusingascript,useathird-partytoollikeProduKey,orcheckyouremailorreceipt.First,fortheregistrymethod:openNotepad,pastetheprovidedscript,saveitasproductkey.vbs,andrunittodisplayyourkeyinamessagebox—noteth
Jul 03, 2025 am 12:15 AM
Hot tools Tags
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
vc9-vc14 (32+64 bit) runtime library collection (link below)
Download the collection of runtime libraries required for phpStudy installation
VC9 32-bit
VC9 32-bit phpstudy integrated installation environment runtime library
PHP programmer toolbox full version
Programmer Toolbox v1.0 PHP Integrated Environment
VC11 32-bit
VC11 32-bit phpstudy integrated installation environment runtime library
SublimeText3 Chinese version
Chinese version, very easy to use
