remove enclosing brackets from a file

Question

How can I efficiently remove enclosing brackets from a file with bash scripting (first occurrence of [ and last occurrence of ] in file)? All brackets that are nested within the outer brackets and may extend over several lines should be retained. Leading or trailing whitespaces may be present.

content of file1

[
  Lorem ipsum
  [dolor] sit [amet
  conse] sadip elitr
]

cat file1 | magicCommand

desired output

  Lorem ipsum
  [dolor] sit [amet
  conse] sadip elitr

content of file2

  [Lorem ipsum [dolor] sit [amet conse] sadip elitr]

cat file2 | magicCommand

desired output

  Lorem ipsum [dolor] sit [amet conse] sadip elitr

So the ones you want removed are always the first and last characters of the file (Not counting leading/trailing whitespace)? — Shawn, Jun 29 '21 at 23:25

score 3 · Accepted Answer · answered Jun 30 '21 at 00:16

If you want to edit the file to remove the braces, use ed:

printf '%s\n' '1s/^\([[:space:]]*\)\[/\1/' '$s/\]\([[:space:]]*\)$/\1/' w | ed -s file1

If you want to pass on the modified contents of the file to something else as part of a pipeline, use sed:

sed -e '1s/^\([[:space:]]*\)\[/\1/' -e '$s/\]\([[:space:]]*\)$/\1/' file1

Both of these will, for the first line of the file, remove a [ at the start of the line (Skipping over any initial whitespace before the opening brace), and for the last line of the file (Which can be the same line as in your second example), remove a ] at the end of the line (Not counting any trailing whitespace after the close bracket). Any leading/trailing whitespace will be preserved in the result; use s/...// instead to remove them too.

score 1 · Answer 2 · answered Jun 30 '21 at 01:10

1

perl -0777 -pe 's/^\s*\[\s*//; s/\s*\]\s*$//' file

That's aggressive about removing all whitespace around the outer brackets, which isn't exactly what you show in your desired output.

answered Jun 30 '21 at 01:10

glenn jackman

238,783
38
220
352

as I do not need the leading or trailing whitespaces your solution is also exciting, especially as it is even shorter than using `sed` ... thanks – jpseng Jun 30 '21 at 11:16
This will be more memory intensive than the sed call: this perl will read the entire file into memory, the sed reads a line at a time. If your files are not large, then this will be faster. – glenn jackman Jun 30 '21 at 12:41

score 1 · Answer 3 · answered Jul 04 '21 at 20:06

1

With GNU sed for -E and -z:

$ sed -Ez 's/\[(.*)]/\1/' file1

  Lorem ipsum
  [dolor] sit [amet
  conse] sadip elitr

$ sed -Ez 's/\[(.*)]/\1/' file2
  Lorem ipsum [dolor] sit [amet conse] sadip elitr

The above will read the whole file into memory.

answered Jul 04 '21 at 20:06

Ed Morton

188,023
17
78
185

1

I never noticed the option `-z` before ... thanks for this tip – jpseng Jul 04 '21 at 20:25

remove enclosing brackets from a file

3 Answers3