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How do I remove control characters?

by Grunk (Initiate)
on May 07, 2002 at 21:30 UTC ( #164831=categorized question: print w/replies, xml ) Need Help??
Contributed by Grunk on May 07, 2002 at 21:30 UTC
Q&A  > regular expressions


Description:

I have a korn shell at work that strips all the control characters (octal 041-176). I'm trying to write a job in perl to do the same to do some speed comparisons.

My question is, how do I specify to sub a range of octal values to a space (default)?
something like
s/!(octal value 041-176)/ /g

Answer: How do I remove control characters?
contributed by jsprat

Try perldoc perlop and look for the transliteration operator.

tr/\040-\176/ /c;
The 'c' option means complement the range.
Note: you may have to binmode the filehandle, depending on your OS.
Answer: How do I remove control characters?
contributed by tachyon

tr/// is better but all you needed to make your pseudocode real perl code was:

s/[^\040-\176]/ /g

Note that the control chars are \000 - \037 so these are perhaps more direct:

tr/\000-\037/ /; # best option for speed s/[\000-\037]/ /g # but this still works

Note chr 32 dec 040 octal is the space so you were double spacing your spaces by starting at \041

Answer: How do I remove control characters?
contributed by kgsz

For similiar problem (removing colors):

For shell:

cat something | perl -le 'while (<>) {chomp; s/[\000-\037]\[(\d|;)+m// +g; print ($_) };'

In generic:
# sth; sth; { s/[\000-\037]\[(\d|;)+m//g; } # sth else;
ANSI colors looks like :) ^[[number[;number]m - reset: ^[[m

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    [oiskuu]: The useful bits that relate to your process can be found under /proc/self. What information are you thinking of? Tty name?
    [tye]: I just daemonized and getlogin() still knew who I had been.
    [tye]: perhaps loginuid ? Not that I concede that something not being in /proc means it is not useful.
    [Corion]: tye: That's really interesting, but maybe it is because getlogin() returns the name, or the uid, so if that user has been replaced by another user with the same uid in the meantime, that's no problem to the system...
    [davido]: or on ubuntu /var/run/utmp
    [Corion]: Otherwise, I would imagine that a user with a process still alive would lock that information in memory.
    [davido]: so last -f /var/run/utmp on ubuntu provides similar (though more verbose) info
    [oiskuu]: glibc getlogin just does ttyname() and falls back on getutline(); it's not security related at all. (reminds me of sendmail and remote finger services of the naive early spam era)
    [Corion]: But yes, "who started this process" is interesting information :)
    [tye]: no, I really believe that "login user" was added as a fundamental bit of info about each process in order to enhance the usefulness of auditing

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