Category Archives: Command Line FU

Command Line FU Tips and Tricks

Using grep to search a file using multiple words as boolean AND OR condition

Posted on September 10, 2024 by dsg_admin
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Use sed to replace last character after matching a line

Posted on May 14, 2024 by dsg_admin

If you are a coder like me we tend to discover after we have made a script that we need to change something on multiple lines. Recently I have a script whereby added a “log_message” function which would echo a … Continue reading →

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Viewing contents of an open filehandle on a deleted file

Posted on May 1, 2024 by dsg_admin

There are times when you may unintentionally delete a file which is being written to. When this occurs it will leave an Open Filehandle. In Linux open filehandles may be viewed via the ‘lsof’ command. # lsof +L1 In the … Continue reading →

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Cscope search results are invisible

Posted on February 13, 2024 by dsg_admin

Part of my ‘day job’ is trolling thru source code when looking for answers. My preferred mechanism, other than a recursive grep, is to use cscope Cscope is a useful tool for searching a source code tree after you build … Continue reading →

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Display ethernet devices on a Fedora system using the Linux Pseudo Filesystem and create a static IP Address

Posted on September 11, 2023 by dsg_admin

Encountered a fun riddle recently whereby on a Fedora 34 system I needed to locate all ethernet interfaces on a system that are obtaining a DHCP address, then after the first reboot create a static IP address. I am a … Continue reading →

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Downloading an RPM package including all of its dependencies on Fedora

Posted on September 8, 2023 by dsg_admin

There are times when you need to fully download an RPM and all of its dependencies. However, If you have already downloaded the RPM re-downloading the RPM and all its dependencies can be very difficult. I have found the following … Continue reading →

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Remove any potential special characters or spaces from an IP address using AWK

Posted on July 12, 2023 by dsg_admin

Got stuck earlier in an interesting regex mystery and I command-line FU’d an AWK Solution. PROBLEM I want to strip out all spaces and/or special characters from an IP address PROCESS I know how to validate an IP address no … Continue reading →

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Using AWK to print N lines up until the FIRST MATCH of a string and then exit

Posted on July 1, 2022 by dsg_admin

Often you are looking for a keyword within a log file but you need to print out X lines BEFORE the first match of a string, THEN exit the search. There are many ways to skin a cat, and here … Continue reading →

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Telnet to a port on a remote machine without ncat or telnet, or nmap

Posted on May 19, 2022 by dsg_admin

There are situations where you may be working on Linux based system, and telnet, ncat or nmap does not exist. In Linux, you can route a test thru the protocol, destination IP address, and destination  port using the “/dev” linux … Continue reading →

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sed print only line AFTER string match

Posted on May 19, 2022 by dsg_admin

File Example

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