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I have this file. I want to use only sed, no awk
FSDFDSFSD
FDSFD
FHGDHFDHGHFGHGHGF
HHGDF
GFDGDFGFDG
GFDGFDGFDGDFGDGD
I want to fill every odd line appended with 000 so that total characters are 30 in each line
I want output like
FSDFDSFSD0000000000
FDSFD
FHGDHFDHGHFGHGHGF00
HHGDF
GFDGDFGFDG000000000
GFDGFDGFDGDFGDGD
One way:
sed -e :a -e 's/^.\{1,29\}$/&0/;ta' -e n file
Match any character(.), and match 1 to 29 characters of the same type(1,29). If match successful, put a '0' behind the pattern matched(&). When the match fails which means when the count of characters excluding the first character exceeds 29, stop it and hence we get the string zero padded by 30.
n at the end simply reads the next line and prints it. This way the even numbered lines get printed untouched.
Executing the above script:
$ sed -e :a -e 's/^.\{1,29\}$/&0/;ta' -e n file
FSDFDSFSD000000000000000000000
FDSFD
FHGDHFDHGHFGHGHGF0000000000000
HHGDF
GFDGDFGFDG00000000000000000000
GFDGFDGFDGDFGDGD
00000000000000000000 FDSFD 000000000000HGHGF HHGDF 0000000000000000000 GFDGFDGFDGDFGDGD
Another approach:
sed 's/$/000000000000000000000000000000/;s/\(.\{30\}\).*/\1/;n'
That would be faster than the iterative approach at appending one character at a time, but note that it would truncate lines that were longer than 30 characters in the first place.
