## substitute the first 't' to 'T' sed 's/t/T/' file ## substitute all 't' to 'T' sed 's/t/T/g' file
## substitute 'all little letters' to 'T' sed 's/[a-z]/T/g' file ## similarly, you can substitute 'all numbers' to 'T' sed 's/[0-9]/T/g' File
Deleted matched line
sed '/pattern/d' filename
sed '1d' filename # deleted the first line only sed '2d' filename # deleted the second line only
Adding a line
## adding a line before the matched line sed -i '/allow chengyongxu.com/i\allow chengyongxu.cn' file ## adding a line after the matched line sed -i '/allow chengyongxu.com/a\allow chengyongxu.cn' file
Match pattern
Pattern
Meanings
Example
Result
^
The begin of each line
sed '/^A/d' file
Delete all lines which begin with ‘A’
$
The end of each line
sed 's/$/+/' file
Add a ‘+’ at the end of all lines
[ ]
match all single elements in it
sed 's/[abcd]/T/g' file
Replace all ‘a’, ‘b’, ‘c’, and ‘d’ to ‘T’
Sed
sed 's/^t/000/g' filename #the t on beginning of the lines replaced by *** sed 's/t$/000/g' filename #000 as a substitute for the t on the end of the lines
sed 's/[0-9]/*/' filename # * as a subustitute for every number with *
sed 's/[a-z][A-Z]/--/' filename # looking for a pattern that a lower capital followed a capital ## TaT --> T--
sed 's/[a-zA-Z]/--/g' filename # -- as a substitute for all letters on the filename or sed 's/[a-Z]/--/g' filename
sed 's/[0-z]/--/g' filename
sed 's/[0-9]/-&-/g' filename # exp: 833 new -- > -8--3--3- new sed 's/[0-9][0-9]/-&-/g' filename # exp: 833 new -- > -833- new
sed 's/\w/_/g' filename # or letters except symples.(including chinese)
sed 's/\b/==/g' filename # add a "==" on the begin and the end of all words ## ==4811== ==that== [==ðæt==; ==ðət==]
sed 's/[^0-9]/*/g' filename # ^ means negated match
sed 's/A/B/g;s/C/D/f' FILENAME
############################# ### deleted the match line ## #############################
sed '/\bnew\b/d' filename #boundary (new),( new),(new ),( new ),( new, )
sed '/^$/d'# remove the line which beginning with end (blank line)
sed '5,$ d' filename equo sed '4 q' filename equo head -n 4 filename
