CODEWITHSUNDEEP
awk
user12331
user12331

Reputation: 518

Append a character depending upon the length

I have a list of lines like 

50000
12345
2345
12341
3456

I want to append a character 0 at the beginning to the lines having only 4 characters so that the result is something like this

50000
12345
02345
12341
03456

How can I do it efficiently. Don't ask me to use a loop. Is there anything using awk.

Upvotes: 0

Views: 92

Answers (2)

Jonathan Leffler
Jonathan Leffler

Reputation: 753725

It is tempting to suggest:

awk '{printf "%05d\n", $1}' file

This prints the first field of the file as a zero-padded 5-digit number. It will handle inputs such as 1, 23, 456 as well as 2345 (producing 00001, 00023, 00456, 02345). However, it does assume that the inputs are all numbers; it will not work so well if they're alphanumeric strings, for example.

Upvotes: 4

jaypal singh
jaypal singh

Reputation: 77105

You can use the length() function of awk. 

$ awk 'length($0)==4{$0=0 $0}1' file
50000
12345
02345
12341
03456

We use the pattern length($0)==4 to check if the line is 4 characters long. If it is we append 0 in front of it. 1 allows us to print the lines that don't match our criteria as is.

Upvotes: 3

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