Command line workshop notes

README

				man

* man grep
* apropos uname

			if, then, else, fi

* -e (file exists)
* -d (file is directory)
* -z (string is empty)
* -N (modified after last read)
* -gt, -lt, -eq, -ne, ...

$ if [ -d / ]; then echo "/ is a directory."; fi

$ [ -e README ]

$ if [ $? -eq 0 ]; then
	echo ":-)"
else
	echo ":'|"
fi

			for, in, do, done

$ for file in $(ls); do echo $file; done

$ for line in $(cat README); do
	echo $line | grep -q "*"
	if [ $? -eq 1 ]; then
		echo $line
	fi
done

$ grep -v "*" README

			Intermezzo - Run Daemon

	#!, sleep, cat << EOF, File Streams (>, >>), Daemons

$ cat daemon.sh
#!/bin/sh

while [ 1 ]; do
	for file in $(find . -name "*.py"); do
		if [ -N $file ]; then
			echo "$file has been updated, executing..."
			python $file
		fi
	done
	sleep 1
done
$ chmod +x daemon.sh && ./daemon.sh &
$ cat << EOF > hello.py
#!/usr/bin/python

print("Hello world.")
EOF

			Intermezzo - Factorial

	variables, $(), while loops, math, read, arguments, chmod

$ cat factorial.sh
#!/bin/sh

n=$1

if [ -z $n ]; then
	echo -n "Enter a number: "
	read n
fi

factorial=1
while [ $n -gt 0 ]; do
        factorial=$(( $factorial * $n ))
        n=$(( $n - 1 ))
done    
echo $factorial

$ chmod +x factorial.sh
$ ./factorial.sh 7
$ ./factorial.sh

				grep

* -q 	(quiet)
* -r 	(recursive)
* -i 	(case insensitive)
* -v 	(inverted match)
* -n 	(print line number)
* -o 	(only matching)
* -C 	(with context lines)
* -P 	(with perl-style regex)

Pick any corpus of text you have available, any project, and play with it.

				regex

* <regex> | <char-class> | <special-char>
* 
* <regex> :
* 	R?
* 	R+
* 	R*
* 	R{n}
* 	R{n,}
* 	R{n,k}
* 	R{,k}
* 	R|R
* 	(R)
* 	^R
* 	R$
*
* <char-class> :
* 	[...]
* 	[^...]
*
* <special-char> : \{, \}, \(, \), ., ...
*
* Back References : (...) -> \n

$ grep -Po "\d"
$ grep -Po "[A-Z]+"
$ grep -Po "[0-9]*"
$ grep -Po "[a-z]{5}"
$ grep -Po "^Hello"
$ grep -Po "Hello$"
$ grep -Po "^Hello$"
$ grep -Po "I am (\w+) you are \1."
I am glad you are sad.

I am very sad you are sad.

I am happy you are happy. 
I am happy you are happy.

				sed

* s/foo/bar/g
* -i

$ sed 's/    /\t/g'

				find

* -name R
* -type f|d
* -exec 
 	find /tmp -exec echo {} \;
 	find ~/projects/misc-python -name "*.pyc" -exec rm {} \;

				Appendix

* http://tldp.org/LDP/abs/html/refcards.html

Reminder: cover screen's Ctl+A+C, Ctl+A+A, Ctl+A+"