Command-Line – How to Insert a Space Every Four Characters in a Long Line

command lineshelltext processing

I've got a long line that I want to insert a space every 4 characters, on a single lone line of solid text to make it easier to read, what's the simplest way to do this? also I should be able to input the line from a pipe. e.g.

echo "foobarbazblargblurg" | <some command here>

gives

foob arba zbla rgbl urg

Best Answer

Use sed as follows:

$ echo "foobarbazblargblurg" | sed 's/.\{4\}/& /g'
foob arba zbla rgbl urg

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Linux – How to do multiline search and replace text (delete) recursively

Sed can do a lot of things beside simple search-and-replace, and that includes multiline support.

Here's a blog post on how someone did this (he wrote a sedml script for "sed multiline": http://austinmatzko.com/2008/04/26/sed-multi-line-search-and-replace/

The basic idea is to copy the whole file to sed's "hold buffer", run the regex on that and then write out the changed file. However, this approach may be rather slow if your files are large as you're loading a whole file at a time into memory.

How to insert text after the last configuration line

You could do something along these lines:

file=/some/file
newtext='sol { mass = 42, start = 9.2 }'
tac -- "$file" | 
  NEWTEXT=$newtext awk -v size="$(wc -c < "$file")" '
    $1 ~ /^[^#]/ {
      system("dd bs=1 seek=" size - length(footer) " conv=notrunc if=/dev/null")
      printf "%s\n%s", ENVIRON["NEWTEXT"], footer
      exit
    }
    {footer=$0 "\n" footer}' 1<> "$file"

That overwrites the file in place and only stores the footer in memory. It needs the non-standard GNU tac command. The file has to be a regular text file.

Best Answer

Related Solutions

Linux – How to do multiline search and replace text (delete) recursively

How to insert text after the last configuration line

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