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Linux

Bash Check If Shell Is Interactive or Not Under Linux / Unix Oses

How do I check in GNU/Bash if a shell is running in interactive mode or not while writing shell scripts?
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Grep Include Only *.txt File Pattern When Running Recursive Mode

I'm using Debian Linux as my development workstation. I would like to search a directory called ~/projects/ recursively for "foo" word only for *.txt files. How do I search all text files in ~/projects/ for "foo" word using grep command?
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Linux dd Command Show Progress Copy Bar With Status

I'm using dd command for block level copy and just found out that there's no built in way to check the progress. How do I use the Linux or Unix dd command while coping /dev/sda to /deb/sdb and display a progress bar when data goes through a pipe?
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HowTo: Use Grep Command In Unix / Linux To Search Subdirectories

I would like to search and find all files which contain a word called "main()" for all directories located in $HOME/project/school. How do I use the grep command to find text including all subdirs under Unix or Linux operating systems?
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HowTo: Revoke OpenSSH Keys and Disable User Access

Many users are using ssh to log into a remote machine and append the indicated identity file to machine's ~/.ssh/authorized_keys file. I recently moved one of my server, and I would like to revoke openssh keys and disable user access under Linux operating systems. How do I revoke OpenSSH keys under Unix or Linux operating systems?
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Linux / Unix: sed Command Print Only Matching Lines

I see many examples and man pages on how to do operations like search-and-replace using sed. But, I want to match a given string or a regular pattern expression and display on the screen. How do I print lines with matching pattern using sed command only under Unix like operating systems?
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Synology Nas: Run Fsck To Check and Repair a Linux File System

I own a Linux powered Synology dedicated Network Attached Storage (NAS) server for my home office use. How do I run fsck on Synology DiskStation that offers RAID storage using Linux command line options over an ssh session?
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Unix / Linux: Maximum Character Length of Arguments In a Shell Command

What is the maximum character length of arguments in a shell command? How do I find out the maximum length of arguments for a new process under Linux or Unix like operating systems?
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Linux / Unix: Find Out DNS Server IP Address / Names

How do I find out my DNS server IP address assiged my my ISP under Unix or Linux operating system using command prompt? How do I find preferred dns server under Debian / Ubuntu / Fedora Linux desktop system?
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Linux: warning: CUPSEXT could not be loaded. Please check HPLIP installation.

I'm trying to install latest version of Hewlett-Packard's Linux Imaging and Printing software (HPLIP) for my office jet printer. In order to install latest version of HPLIP I removed the hplip-gui, hplip, hplip-cups, hplip-data, hpijs, and hpijs-ppds Debian Linux packages However, I'm getting the following error:

Debian warning: CUPSEXT could not be loaded. Please check HPLIP installation.

How do I fix this error while installing hplip-3.12.9.run under Debian Linux 6.0.5 amd64 bit?
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