FAQs

With Bash to explicitly declare an array you have to use

declare -A mioarray

To have the value of element 5 just write

echo ${mioarray[5]}

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To redirect the standard error of a shell command, just use the following syntax:

ls file-that-does-not-exist 2>&1 | grep file

Or even better not to have on the terminal the standard error just throw it in /dev/null

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Suppose you want to rename the name of a group of files that have the following template:

file1_tmp.sh
file2_tmp.sh
...
file99_tmp.sh

and suppose you want to remove the '_tmp' middle part in all the files. We can use the command "rename" or "prename":

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Suppose you only want to print a single line of a file, which for convenience is indicated by line 25

perl -ne '$. == 25 && print && exit' file.txt

Of course if we also want to print lines 31 and 57

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Suppose you have a "test encode" string and a "prova.txt" file you want to encode in Mime base64. To solve the problem we can simply launch the command line:

perl -MMIME::Base64 -e 'print encode_base64("test encode")'
perl -MMIME::Base64 -0777 -ne 'print encode_base64($_)' prova.txt

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Suppose we have a text file (prova.txt) that we want to number. We can use:

perl -pe '$_ = "$. $_"' prova.txt

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$str =~ s/(\d+)/$1+1/ge

Suppose you have a file named "file-with-keys-gpg" and want to extract it by deleting any other line in the file.

perl -ne 'print if /-----BEGIN PGP PUBLIC KEY BLOCK-----/../-----END PGP PUBLIC KEY BLOCK-----/' file-with-keys-gpg

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