2

How can I indent a file such as its first line?

Example:

A file containing

     x=1+2+3+4+
5+6+7+8
+9+10+12

should be converted to

     x=1+2+3+4+
     5+6+7+8
     +9+10+12

I need this inside a shell-script on a Linux system. One-liners are preferred.

  • does the first line always start with x=? – amphibient Dec 13 '12 at 16:44
  • @foampile no, just an example – jofel Dec 13 '12 at 16:48
  • are you limited to shell or can you use a scripting language? – amphibient Dec 13 '12 at 16:53
  • @foampile I can use any common script language. Speed is less important. – jofel Dec 13 '12 at 17:03
  • i was gonna suggest Perl. @Birei below posted a good answer. albeit i am increasingly liking awk as well – amphibient Dec 13 '12 at 17:07
5

One way using perl:

perl -pe 'if ($. == 1) { m/^(\s*)/; $space = $1 || q{}; next } s/^\s*/$space/' infile

It yields:

    x=1+2+3+4+
    5+6+7+8
    +9+10+12
5

You can do this in awk:

awk 'NR==1{split($0,a,/[^ \t]/)}{sub(/^[ \t]*/,a[1]);print}' file.in
2

With sed:

sed -e '1{h;s/[^[:blank:]].*//;x;b' -e '}' -e 'G;s/[[:blank:]]*\(.*\)\n\(.*\)/\2\1/'

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