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I found a question about, how to remove lines longer then 2048 chars:
How to delete line if longer than XY?
Q: But how can I remove lines shorter then 4 chars? So remove lines that has 1 or 2 or 3 length in a file.
UPDATE: Thanks for the many GOOD answers, but I can only mark one as OK
You could use sed. The following would remove lines that are 3 characters long or smaller:
sed -r '/^.{,3}$/d' filename
In order to save the changes to the file in-place, supply the -i option.
If your version of sed doesn't support extended RE syntax, then you could write the same in BRE:
sed '/^.\{,3\}$/d' filename
which would work with all sed variants.
You could also use awk:
awk 'length($0)>3' filename
Using perl:
perl -lne 'length()>3 && print' filename
sed '/^.\{,3\}$/d' doesn't work with BSD sed: sed: 1: "/^.\{,3\}$/d": RE error: invalid repetition count(s). The sed -r version is syntactically valid, but won't remove lines.
Feb 18, 2018 at 14:50
Some more variations:
grep .... file
or
sed '/..../!d' file
or
sed -n 's/./&/4p' file
or
awk 'gsub(/./,"&")>3' file
or
awk 'length>3' file
or GNU awk:
awk 'NF>3' FS= file
Here is the Vim solution using Vim's Ex mode and the global command.
This is very similar to using sed, only that some special chars ('{', '}') need to be escaped.
:g/^.\{,3\}$/d
Using Vim's Very Magic Regex mode (\v), this escaping can be avoided.
:g/\v^.{,3}$/d
See also :help magic
Use of "\v" means that in the pattern after it all ASCII characters except
'0'-'9', 'a'-'z', 'A'-'Z' and '_' have a special meaning. "very magic"
Also sometimes useful is to do the opposite with vglobal.
:v/\v^.{,3}$/d
would delete everything but lines till 3 chars.
You can use grep:
If you count leading spaces in line length:
grep -e '[^\ ]\{4,\}' file
If you don't count leading spaces in line leangth:
grep -e '[^\]\{4,\}' file
to directly remove the lines you could:
sed -ri '/.{4}/!d' /path/to/file
Or BRE:
sed -i '/.\{4\}/!d' /path/to/file
If a line does not contain 4 or more characters it is deleted.
f=/path/to/file
cat <<GREP >"$f"
$(grep -E ".{4}" "$f")
GREP
Doing the above in command-substitution subshell will ensure that grep gets a read descriptor on it before cat starts writing to it, but the <<HEREDOC will also ensure that the result remains streamed and does not cause argument length errors.
sed '/^.\?.\?.\?$/d' input.txt > output.txt
