Procesando archivos en pararelo en bash con "xargs"

function process_file {
file=$1
do_something_with $file
}
export -f process_file


find PATH -type f | xargs --max-args=1 --max-procs=NUM -I{} bash -c process_file \{\}
or a shorter version
find PATH -type f | xargs -n1 -PNUM -I{} bash -c process_file \{\}



Where NUM is the number of parallel jobs and PATH where to start looking for the files.


source

copy files to another machine using tar

tar cf - * | ssh user@host "(cd /destination_dir; tar xf -)"

Get list tables from postgres database

If we need to iterate over all tables of a certain schema, we can get the list of schema, table, type and user using psql:

$ psql -qAtF, -c "\dt da_schema.*"
da_schema,segments,table,jacen
da_schema,speeds,table,jacen
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You can also use "*" in the schema name, for example:

$ psql -qAtF, -c "\dt da_schema*.*"
da_schema,segments,table,jacen
da_schema,speeds,table,jacen
da_schema_2,labels,table,jacen
da_schema_test,positions,table,jacen
$ _

Changing execution attributes on svn

Sometimes a script is added to a SVN repository without execution permissions. After that, a simple chmod doesn't work for SVN.

This is what can be done to change the attributes of the file:

$ svn propset svn:executable on da_scripto.sh
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Attach a file to a mail on shell

In the old times we were able to attach a file using the mail command. Now, we can do the same thing using mutt:

$ echo "Mail body" | mutt -s "This is a mail with attachments" -a ~/mi_file.txt -a ~/mi_picture.png anne@octop.us
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We can also use some pre-written file to use as the email body:

$ mutt -s "Mail with body from a file" anne@octop.us < ~/mail_body.txt
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Get IP address of a host

If you need to get the IP address of a host, but you don't want to parse the output of ifconfig, you can use hostname:

$ hostname -i
192.168.1.160
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Error handling in Bash

To check if a command was successfully run in our bash script, we have to check the value of its output, which is stored in the $? variable. If its value equals to 0, then the command was successful, otherwise, an error was thrown:

rm ~/data.tar.bz2
if [ "$?" != 0 ]; then
   echo "ERROR: Could not delete file"
   exit 1
fi

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