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Unable to grep control/non printable characters

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Top Forums Shell Programming and Scripting Unable to grep control/non printable characters
# 8  
Old 02-01-2012
Wow, I've never seen that behavior anywhere. I can only guess that shell was made for a system that didn't always have the | key Smilie
# 9  
Old 02-01-2012
I found a reference to it here: https://en.wikipedia.org/wiki/Thompson_shell.
It would seem that Bourne kept it for compatibility with the Thompson shell I guess.

It's mentioned here too in the Thompson shell man page: http://www.in-ulm.de/~mascheck/bourne/v4/
search for the circumflex character '^'.

"One or more commands separated by '|' or '^' constitute a pipeline."

Look at this even older Thompson shell version, where pipe symbols were the same as redirection: http://www.in-ulm.de/~mascheck/bourne/v3/

By extending the syntax used for
redirection of I/O, a command line can specify that the
output produced by a command be passed via a pipe through
another command which acts as a filter. For example:

 command >filter>
Last edited by gary_w; 02-01-2012 at 12:55 PM..
# 10  
Old 02-03-2012
Data
Quote:
Originally Posted by Corona688
^ and * have special meanings in perl regular expressions, too.

Escape them!
The problem is that "^^^613*" will be stored in a variable(i) like
Quote:
while read i
do
pearl -pi -e "s|$i|$passwd|g" $k
done


How will the script understand when will $i contain a special character and escape that automatically
# 11  
Old 02-04-2012
Hi.
Quote:
Originally Posted by Corona688
Wow, I've never seen that behavior anywhere. I can only guess that shell was made for a system that didn't always have the | key Smilie
Yes, like TTY33's -- ASR-33 Teletype - Wikipedia, the free encyclopedia -- limited character set, uppercase only, slow, noisy, etc., adapted for interactive work from other environments ... cheers, drl
# 12  
Old 02-04-2012
For grepping use fgrep:
Code:
$ i="^^^613*"
$ echo "$i"
^^^613*
$ echo '/test/x201.cfg:reg.1.random="^^^613*"' | fgrep "$i"
/test/x201.cfg:reg.1.random="^^^613*"

A quick and dirty way to escape these special characters:
Code:
perl -pi -e "s|$(printf "%s" "$i"|sed 's/[*^]/\\&/g')|$passwd|g" "$k"
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