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Chaining Linux Commands Together

Feb 03, 2009, 01:32 (0 Talkback[s])

[ Thanks to Brandon for this link. ]

"What if you wanted to run a command and when it finished, run another? Linux provides three ways to do this with a slightly different end result. The semicolon (;), ampersand (&) and the verticle pipe (|) all help the user "chain" commands together.

"[user@localhost ~]$ apt-get update ; apt-get upgrade

"In this example we are using the semicolon (;) to separate these two commands. Using a semicolon tells the shell, "once the first command finishes, run the second one". Once apt-get update finishes, the system will then run it again using the upgrade option.

"[user@localhost ~/project1]$ ./configure && make && make install

"This command is mainly used by developers, software package maintainers and Linux power users. This chain of commands compiles a program and installs it. What the double-ampersands are telling the system is "wait for the first command to successfully complete. If it does complete successfully, run the next command".

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