topic Re: use of cut in command in Operating System - Linux

use of cut in command

Gesmundo — Mon, 06 Feb 2017 04:41:08 GMT

Can anybody see the issue?
I have the following commands:
$ x3=$(grep -i isend x.x | tr -s " " )
$ echo $x3
isEndOfStream = false
$ x3=$(grep -i isend x.x | tr -s " " | cut -d "=" -f 2 )
$ echo $x3
false
$ x3=$(grep -i isend x.x | tr -s " " | cut -d "=" -f 2 | cut -c1-5)
$ echo $x3
fals

Where is 'e'?

But if I further do this:
$ x4=$(echo $x3)
$ echo $x4
false
$ x4=$(echo $x3 | cut -c1-5)
$ echo $x4
false

I got the whole value (false).
Thanks for any explanation and workaround.

Noel

Re: use of cut in command

Steven Schweda — Mon, 06 Feb 2017 05:33:48 GMT

> Where is 'e'?

   Your "cut -c1-5" command cut it off from " false".

pro3$ x3='isEndOfStream = false'
pro3$ echo "$x3" | cut -d "=" -f 2
false

(Note: " false" != "false".)

pro3$ x='   xxx   '

pro3$ echo $x
xxx

pro3$ echo "$x"
   xxx

   Guess which one works more like what happens in your pipeline.

   As for a work-around, it depends on how you'd like to get rid of that
extra space. As usual, many things are possible (once you see the extra
space).

Re: use of cut in command

Gesmundo — Tue, 07 Feb 2017 05:58:50 GMT

Thanks Steven for the reply.

I also found out that there is an unprintable character (CR - ASCII 13) at the end of "false" in the file so I still need to use cut to get only the first 5 characters.

$ x=$(grep -i end x.x | tr -s " " | cut -d "=" -f 2)
$ echo $x
false
$ expr length $x
6
$ x1=$(echo $x | cut -c1-5)
$ echo $x1
false

$ expr length $x1
5

Re: use of cut in command

Steven Schweda — Tue, 07 Feb 2017 06:37:49 GMT

> I also found out that there is an unprintable character (CR - ASCII
> 13) at the end of "false" in the file so I still need to use cut to get
> only the first 5 characters.

   You're already using "tr", so it'd be easy to have it translate a CR
("\r") into something more harmless, like, say, a space. And, of
course, "sed" can destroy spaces with ease:

mba$ x='   xxx   '
mba$ echo "$x"
   xxx
mba$ echo "$x" | sed -e 's/ //g'
xxx

   If you really want exactly five characters, then "cut" is fine, but
if you want to trim off spaces and other junk, then counting characters
may not be the best way.