CODEWITHSUNDEEP
regexrbashunixsed
Jeff Kraus
Jeff Kraus

Reputation: 175

Remove a range of escape / non-printable chars in sed

I am working from horrible text data (2GB csv file) which includes practically all escape chars 0x00-0x1F spattered throughout the file. I attempted to read this into R for processing but cannot due to the EOFs (0x04):

    Warning message:
    In scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  :
      EOF within quoted string

So I thought sed would be a good use to remove all the non-printable junk in the file, but there seems to be some strangeness in how to represent the escape chars in the sed syntax. I have tried all of the following which do not seem to work:

Include only specified chars: 

    sed 's/[^a-zA-Z 0-9`~!@#$%^&*()_+\[\]\\{}|;'\'':",.\/<>?]//g' IN.csv > OUT.csv

Identify range of non-printable in decimal or hex: 

    cat IN.csv | sed 's/[\d0-\d31]//g' > OUT.csv

    cat IN.csv | sed s/[$'\x00'-$'\x1F']//g OUT.csv

    cat IN.csv | sed 's/\x00-\x1F//g' > OUT.csv

and using Ctrl-VCtrl-D to produce this:

    cat IN.csv | sed s/^D//g > OUT.csv

All the commands appear to execute, but the resulting file output does not remove the non-printable chars and appears to change the output in ways unexpected.

What I found that DOES WORK is this:

    cat IN.csv | sed 's/'`echo -e "\x04"`'//g' > OUT.csv

or this:

    cat IN.csv | sed 's/\x04//g' > test3.csv

However this only works for a single escape char. Is there a better way to address all of the non-printable chars at the same time in a single range without having to execute 1 command for each non-printable? I assume I must not be entering the syntax for a range properly.

Upvotes: 0

Views: 471

Answers (2)

tale852150
tale852150

Reputation: 1628

You could try awk:

awk '{gsub(/[[:punct:]]/,"")}1' your_file

or try sed:

sed "s/[^a-z|0-9]//g;" orig_file > new_file

or try perl:

perl -pe 's/[^A-Za-z0-9\s]//g' orig_file > new_file

Upvotes: 0

Krzysztof Krasoń
Krzysztof Krasoń

Reputation: 27476

For removal (and transliteration) there is a better tool called tr (translate or delete characters). You can remove non-printable characters using:

cat IN.csv | tr -cd '\11\12\15\40-\176' > OUT.csv

-d - deletes characters mentioned, -c inverts the ranges.

Or using the POSIX [:print:]:

cat IN.csv | tr -cd '[:print:]' > OUT.csv

Upvotes: 2

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