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Every Nth line position # (AWK)
A better way to show the file lines 3n + 1

Change every instance of OLD to NEW in file FILE
Very quick way to change a word in a file. I use it all the time to change variable names in my PHP scripts (sed -i 's/$oldvar/$newvar/g' index.php)

Compare two directory trees.
This uses Bash's "process substitution" feature to compare (using diff) the output of two different process pipelines.

See a full list of compiler defined symbols
From http://lists.debian.org/debian-devel/2001/01/msg00971.html .

open two files on top of each other in vim (one window, two panes)

Create a single-use TCP (or UDP) proxy
Redirect the local port 2000 to the remote port 3000. The same but UDP: $ nc -u -l -p 2000 -c "nc -u example.org 3000" It may be used to "convert" TCP client to UDP server (or viceversa): $ nc -l -p 2000 -c "nc -u example.org 3000"

Write on the console without being registered
http://www.linux-party.com/index.php/8157-escribir-en-la-consola-linux-sin-que-quede-registrado-en-el-history

Find and list users who talk like "lolcats"
Greps IRC logs for phrases and lists users who said them.

Show a config file without comments
Shows a file without comments (at least those starting by #) - removes empty lines - removes lines starting by # or "some spaces/tabs then #'" Useful when you want to quickly see what you have to customize on a freshly installed application without reading the comments that sometimes are a full 1000 lines documentation :) While posting, I saw this http://www.commandlinefu.com/commands/view/1041/display-contents-of-a-file-wo-any-comments-or-blank-lines But it's dirty and incomplete, to my mind My original goal was to remove lines like "\t*#" but I can't figure out how to do a egrep '\t' on a command-line. Two workarounds if needed: $egrep -v 'press control + V then TAB then #' /your/file or $egrep -v -f some_file /your/file #where some_file contains what you want to exclude, example a really inserted TAB

Capture data in ASCII. 1500 bytes
Sniffing traffic on port 80 only the first 1500 bytes


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