Sed

Sed

Remove the 1st line

sed 1d filename

Remove the first 100 lines (remove line 1-100)

sed 1,100d filename

Remove lines with string (e.g. 'bbo')

sed "/bbo/d" filename
# case insensitive:
sed "/bbo/Id" filename

Remove lines whose nth character not equal to a value (e.g. 5th character not equal to 2)

sed -E '/^.{5}[^2]/d'
#aaaa2aaa (you can stay)
#aaaa1aaa (delete!)

Edit infile (edit and save to file), (e.g. deleting the lines with 'bbo' and save to file)

sed -i "/bbo/d" filename

When using variable (e.g. $i), use double quotes " "

# e.g. add >$i to the first line (to make a bioinformatics FASTA file)
sed "1i >$i"
# notice the double quotes! in other examples, you can use a single quote, but here, no way!
# '1i' means insert to first line

Using environment variable and end-of-line pattern at the same time.

# Use backslash for end-of-line $ pattern, and double quotes for expressing the variable
sed -e "\$s/\$/\n+--$3-----+/"

Delete/remove empty lines

sed '/^\s*$/d'

# or

sed '/^$/d'

Delete/remove last line

sed '$d'

Delete/remove last character from end of file

sed -i '$ s/.$//' filename

Add string to beginning of file (e.g. "[")

sed -i '1s/^/[/' file

Add string at certain line number (e.g. add 'something' to line 1 and line 3)

sed -e '1isomething -e '3isomething'

Add string to end of file (e.g. "]")

sed '$s/$/]/' filename

Add newline to the end

sed '$a\'

Add string to beginning of every line (e.g. 'bbo')

sed -e 's/^/bbo/' file

Add string to end of each line (e.g. "}")

sed -e 's/$/\}\]/' filename

Add \n every nth character (e.g. every 4th character)

sed 's/.\{4\}/&\n/g'

Concatenate/combine/join files with a seperator and next line (e.g separate by ",")

sed -s '$a,' *.json > all.json

Substitution (e.g. replace A by B)

sed 's/A/B/g' filename

Substitution with wildcard (e.g. replace a line start with aaa= by aaa=/my/new/path)

sed "s/aaa=.*/aaa=\/my\/new\/path/g"

Select lines start with string (e.g. 'bbo')

sed -n '/^@S/p'

Delete lines with string (e.g. 'bbo')

sed '/bbo/d' filename

Print/get/trim a range of line (e.g. line 500-5000)

sed -n 500,5000p filename

Print every nth lines

sed -n '0~3p' filename

# catch 0: start; 3: step

Print every odd # lines

sed -n '1~2p'

Print every third line including the first line

sed -n '1p;0~3p'

Remove leading whitespace and tabs

sed -e 's/^[ \t]*//'
# Notice a whitespace before '\t'!!

Remove only leading whitespace

sed 's/ *//'

# notice a whitespace before '*'!!

Remove ending commas

sed 's/,$//g'

Add a column to the end

sed "s/$/\t$i/"
# $i is the valuable you want to add

# To add the filename to every last column of the file
for i in $(ls);do sed -i "s/$/\t$i/" $i;done

Add extension of filename to last column

for i in T000086_1.02.n T000086_1.02.p;do sed "s/$/\t${i/*./}/" $i;done >T000086_1.02.np

Remove newline\ nextline

sed ':a;N;$!ba;s/\n//g'

Print a particular line (e.g. 123th line)

sed -n -e '123p'

Print a number of lines (e.g. line 10th to line 33 rd)

sed -n '10,33p' <filename

Change delimiter

sed 's=/=\\/=g'

Replace with wildcard (e.g A-1-e or A-2-e or A-3-e....)

sed 's/A-.*-e//g' filename

Remove last character of file

sed '$ s/.$//'

Insert character at specified position of file (e.g. AAAAAA --> AAA#AAA)

sed -r -e 's/^.{3}/&#/' file