Remove the middle n characters from lines in Bash

问题

I am trying to cut out the middle of each line in a file. All the lines are like this:

79.472850   97 SILENCE

and I need to end up with:

79.472850 SILENCE

As each line has the undesired portion starting at character ten and ending at character 14, I was trying to use sed in this way:

sed "s/$.\{9\}$.\{6\}//" but I just end up with everything after character 14. The numbers following the tab space change in every file. What can I do to make sed just cut out the tab and two digits?

Thanks for your help.

回答1:

As per your input and expected output, this can be a way:

$ echo "79.472850   97 SILENCE" | tr -s " " | cut -d" " -f1,3
79.472850 SILENCE

tr -s " " deletes repeated spaces.
cut -d" " -f1,3 prints 1st and 3rd field based on splitting by spaces.

With sed:

$ sed 's#\([^ ]*\)[ ]*\([^ ]*\)[ ]*\([^ ]*\)#\1 \3#g' <<< "79.472850   97 SILENCE"
79.472850 SILENCE

回答2:

Looks like you need the first and the third fields from the input:

$ echo "79.472850   97 SILENCE" | awk '{print $1, $3}'
79.472850 SILENCE

回答3:

No need to call external programs like sed or cut, or other languages like awk, bash can do it for you:

var="79.472850   97 SILENCE"
echo ${var:0:9}${var:14}
79.472850 SILENCE

${var:0:9} copies 9 characters starting at position 0 (start of text).

${var:14} copies from character position 14 to the end of text.

Alternatively, if it is space-delimited fields you need:

read one two three <<< "$var"
echo "$one $three"
79.472850 SILENCE

Again, that uses pure bash.

回答4:

Here is an awk solution that works even if you have spaces in your third column :

awk '{$2=""; print}' file

Where $2="" empties the second column and print outputs all columns.

回答5:

if you want to extract exactly like what you described with sed:

kent$  echo "79.472850 97 SILENCE"|sed -r 's/(^.{9})(.{4})(.*)/\1 \3/'
79.472850 SILENCE

if you want to extract the 1st and 3rd/last columns, from your space separated input, you could use awk: awk '$2="";7'

kent$  echo "79.472850 97 SILENCE"|awk '$2="";7'
79.472850  SILENCE

来源：https://stackoverflow.com/questions/18186481/remove-the-middle-n-characters-from-lines-in-bash

标签

bash

unix

sed

cut