AWK

awk '{ print $2, $1 }' file # Print and inverse first two columns

awk '{printf("%5d : %s\n", NR,$0)}' file # Add line number left aligned

awk '{print FNR "\t" $0}' files # Add line number right aligned

awk NF test.txt # remove blank lines (same as grep '.')

awk 'length > 80'

SED

sed 's/string1/string2/g' # Replace string1 with string2

sed -i 's/wroong/wrong/g' *.txt # Replace a recurring word with g

sed 's/\(.*\)1/\12/g' # Modify anystring1 to anystring2

sed '/<p>/,/<\/p>/d' t.xhtml # Delete lines that start with <p>

# and end with </p>

sed '/ *#/d; /^ *$/d' # Remove comments and blank lines

sed 's/[ \t]*$//' # Remove trailing spaces (use tab as \t)

sed 's/^[ \t]*//;s/[ \t]*$//' # Remove leading and trailing spaces

sed 's/[^*]/[&]/' # Enclose first char with [] top->[t]op

sed = file | sed 'N;s/\n/\t/' > file.num # Number lines on a file

REGULAR EXPRESSIONS

\^$.|?*+() # special characters any other will match themselves

\ # escapes special characters and treat as literal

* # repeat the previous item zero or more times

. # single character except line break characters

.* # match zero or more characters

^ # match at the start of a line/string

$ # match at the end of a line/string

.$ # match a single character at the end of line/string

^ $ # match line with a single space

^[A-Z] # match any line beginning with any char from A to Z