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Avoiding history file to be overwritten
If histappend options is set in bash, the file .bash_history will not be overwrite and history list is append to it.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

determine if tcp port is open

Printout a list of field numbers (awk index) from a CSV file with headers as first line.
Useful to identify the field number in big CSV files with large number of fields. The index is the reference to use in processing with commands like 'cut' or 'awk' involved.

Quickly Encrypt a file with gnupg and email it with mailx
This is a quick and easy way of encrypting files in a datastream, without ever really creating an output file from gpg. Useful with cron also, when file(s) have to be sent based on a set schedule.

Syntax Highlight your Perl code
This uses Text::Highlight to output the specified Perl file with syntax highlighting. A better alternative is my App::perlhl - find it on the CPAN: http://p3rl.org/App::perlhl

blktrace - generate traces of the i/o traffic on block devices
blktrace is a block layer IO tracing mechanism which provide detailed information about request queue operations up to user space. blkparse will combine streams of events for various devices on various CPUs, and produce a formatted output the the event information. It take the output of above tool blktrace and convert those information into fency readable form.

Tell local Debian machine to install packages used by remote Debian machine
(also works on Ubuntu) Copies the 'install,' 'hold,' 'deinstall' and 'purge' states of packages on the remote machine to be matched on the local machine. Note: if packages were installed on the local machine that were never installed on the remote machine, they will not be deinstalled by this operation.

Test http request every second, fancy display.
Use the command watch, which is really hard to pass nested quotes to, and insert newlines where they are supposed to go in the HTTP request. that is after 1.1 after the host and two newlines at the end before the EOF. i use this all day what? no support for HEREDOCs on commandlinefu's interface? need more fu.

List all packages by installed size (Bytes) on rpm distros


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