Linux

CheatSheet

command	desc
`awk '{print $0}'`	print entire line, 07.46.199.184 [28/Sep/2010:04:08:20] “GET /robots.txt HTTP/1.1” 200 0 “msnbot”
`echo 'this is a test' \vert awk '{print $3}'`	a
`echo 'this is a test' \vert awk '{print $1, (NF-2)}'`	print first and NF number of columns print the second column from end
~awk~
`awk '{print NR ") " $1 " -> " $(NF-2)}' logs.txt`	`NR` Row Number. `1) 07.46.199.184 -> 200`
`awk '{print $2}' logs.txt \vert awk 'BEGIN{FS=":"}{print $1}'`	`FS` separator is :. `[28/Sep/2010`
`sed 's/\[//'`	Remove the first `[`
`awk '{if ($(NF-2) == "200") {print $0}}' logs.txt`	Filter status column with status 200
`awk '{a+=$(NF-2); print "Total so far:", a}' logs.txt`	Variable cross rows sum the total of status numeric column
`awk '{a+=$(NF-2)}END{print "Total:", a}' logs.txt`	Print only last cummulative value
`pipes`
`sbt test \vert& tee ~/tmp/test.log`	console + log

File oriented file system everything is a file.
Every process keeps a table of file descriptors that shows files that are currently in use. Example STDIN STDOUT

ls /proc/$PID/fd/ This is what the process is doing 0 is stdin, 1 is stdout 7,8 network for interprocess communication.

grep -B 1 - grep results one line before.