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I have a text like:
it's like a foo.
it's like a bar.
it's like a bar.
it's like a foo.
I want to remove the indentation or space at the first line and remove the same count of indentation or space in the following lines.
If the following lines space or indentation is less than the count of space or indentation in first line, then remove the all space or indentation at the beginning.
The output is:
it's like a foo.
it's like a bar.
it's like a bar.
it's like a foo.
With expand (to expand TABs into SPCs assuming tab stops every 8 columns; other whitespace characters are not considered) and awk:
<your-file expand | awk -F '[^ ]' '
NR == 1 {n = length($1)}
{sub("^ {1,"n"}", ""); print}'
Using perl:
$ perl -pe 'if($.==1){s/^(\s+)//; $s=length($1);}else{s/^\s{0,$s}//}' file
it's like a foo.
it's like a bar.
it's like a bar.
it's like a foo.
To edit the original file directly, use -i:
perl -i -pe 'if($.==1){s/^(\s+)//; $s=length($1);}else{s/^\s{0,$s}//}' file
perl -lpe 'if($.<2){/^(\s*)/;$s=length $1}s/^\s{0,$s}//' is similar, but handles some edge cases. IRL, I would add some spaces: perl -lpe ' if ($. == 1) { /^(\s*)/; $len = length $1 } s/^\s{0,$len}// '
-l which makes no difference appart from maybe slowing it down imperceptibly. I don't see what edge cases it could catch, what am I missing?
Feels bad to have to start a python interpreter, but it's also an option:
python -c "import textwrap,sys; print(textwrap.dedent(sys.stdin.read()))" < myfile
You could do it with sed, with a little prep-work:
n=$(( $(sed -n '1s/[^[:space:]].*//; p; q' file | wc -c) - 1 ))
sed 's/^[[:space:]]\{1,'"$n"'\}//' file
The first line sets a variable ($n) to the number of leading whitespaces in the first line of the file. The number of bytes that wc sees includes a newline, so we subtract one for that. The second line runs sed with an expression that deletes whitespace from the beginning of the line in a variable amount -- from 1 through $n -- with the \{n,m\} syntax.
Your sed might support an "in-place" edit option (-i).
wc -c counts the number of bytes, not the number of characters, let alone their display width. With GNU wc, you can use wc -L to get the display width of that first line.
Jun 3, 2020 at 17:27