15

I've seen some command like

echo '* - nofile 65535' >> /etc/security/limits.conf

I know echo print something on the screen.

and limits.conf was a file in that /etc/security path.

But want does >> do here? it means something like 'to' or 'in'?

25

>> redirects the output of the command on its left hand side to the end of the file on the right-hand side.

So,

echo '* - nofile 65535' >> /etc/security/limits.conf

will append * - nofile 65535 to the end of the /etc/security/limits.conf file, instead of printing * - nofile 65535 on the screen.

If you instead had

echo '* - nofile 65535' > /etc/security/limits.conf

(note the >> replaced by >), everything already present in /etc/security/limits.conf would have been replaced by * - nofile 65535, and not appended.

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  • 2
    Perfect, especially the extra '>' point. It helps me avoid possible disaster. – Zen May 25 '14 at 6:11

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