在shell的一行中运行多个命令

Question

Say I have a file /templates/apple and I want to

1. put it in two different places and then
2. remove the original.

So, /templates/apple will be copied to /templates/used AND /templates/inuse and then after that I'd like to remove the original.

Is cp the best way to do this, followed by rm ? Or is there a better way?

I want to do it all in one line so I'm thinking it would look something like:

cp /templates/apple /templates/used | cp /templates/apple /templates/inuse | rm /templates/apple

Is this the correct syntax?

Answer 1

You are using | (pipe) to direct the output of a command into another command. What you are looking for is && operator to execute the next command only if the previous one succeeded:

cp /templates/apple /templates/used && cp /templates/apple /templates/inuse && rm /templates/apple

Or

cp /templates/apple /templates/used && mv /templates/apple /templates/inuse

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To summarize (non-exhaustively) bash's command operators/separators:

• | pipes (pipelines) the standard output ( stdout ) of one command into the standard input of another one. Note that stderr still goes into its default destination, whatever that happen to be.
• |& pipes both stdout and stderr of one command into the standard input of another one. Very useful, available in bash version 4 and above.
• && executes the right-hand command of && only if the previous one succeeded.
• || executes the right-hand command of || only it the previous one failed.
• ; executes the right-hand command of ; always regardless whether the previous command succeeded or failed. Unless set -e was previously invoked, which causes bash to fail on an error.

Answer 2

Why not cp to location 1, then mv to location 2. This takes care of "removing" the original.

And no, it's not the correct syntax. | is used to "pipe" output from one program and turn it into input for the next program. What you want is ; , which seperates multiple commands.

cp file1 file2 ; cp file1 file3 ; rm file1

If you require that the individual commands MUST succeed before the next can be started, then you'd use && instead:

cp file1 file2 && cp file1 file3 && rm file1

That way, if either of the cp commands fails, the rm will not run.

Answer 3

Note that cp AB; rm A cp AB; rm A is exactly mv AB . It'll be faster too, as you don't have to actually copy the bytes (assuming the destination is on the same filesystem), just rename the file. So you want cp AB; mv AC cp AB; mv AC

Answer 4

Another option is typing Ctrl+V Ctrl+J at the end of each command.

Example (replace # with Ctrl+V Ctrl+J ):

$ echo 1#
echo 2#
echo 3

Output:

1
2
3

This will execute the commands regardless if previous ones failed.

Same as: echo 1; echo 2; echo 3 echo 1; echo 2; echo 3

If you want to stop execution on failed commands, add && at the end of each line except the last one.

Example (replace # with Ctrl+V Ctrl+J ):

$ echo 1 &&#
failed-command &&#
echo 2

Output:

1
failed-command: command not found

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In zsh you can also use Alt+Enter or Esc+Enter instead of Ctrl+V Ctrl+J

Answer 5

尝试这个..

cp /templates/apple /templates/used && cp /templates/apple /templates/inuse && rm /templates/apple

Answer 6

Using pipes seems weird to me. Anyway you should use the logical and Bash operator:

$ cp /templates/apple /templates/used && cp /templates/apple /templates/inuse && rm /templates/apples

If the cp commands fail, the rm will not be executed.

Or, you can make a more elaborated command line using a for loop and cmp .