如何在当前shell中执行命令的输出？

Question

I'm well aware of the source (aka . ) utility, which will take the contents from a file and execute them within the current shell.

Now, I'm transforming some text into shell commands, and then running them, as follows:

$ ls | sed ... | sh

ls is just a random example, the original text can be anything. sed too, just an example for transforming text. The interesting bit is sh . I pipe whatever I got to sh and it runs it.

My problem is, that means starting a new sub shell. I'd rather have the commands run within my current shell. Like I would be able to do with source some-file , if I had the commands in a text file.

I don't want to create a temp file because feels dirty.

Alternatively, I'd like to start my sub shell with the exact same characteristics as my current shell.

update

Ok, the solutions using backtick certainly work, but I often need to do this while I'm checking and changing the output, so I'd much prefer if there was a way to pipe the result into something in the end.

sad update

Ah, the /dev/stdin thing looked so pretty, but, in a more complex case, it didn't work.

So, I have this:

find . -type f -iname '*.doc' | ack -v '\.doc$' | perl -pe 's/^((.*)\.doc)$/git mv -f $1 $2.doc/i' | source /dev/stdin

Which ensures all .doc files have their extension lowercased.

And which incidentally, can be handled with xargs , but that's besides the point.

find . -type f -iname '*.doc' | ack -v '\.doc$' | perl -pe 's/^((.*)\.doc)$/$1 $2.doc/i' | xargs -L1 git mv

So, when I run the former, it'll exit right away, nothing happens.

Answer 1

The eval command exists for this very purpose.

eval "$( ls | sed... )"

More from the bash manual :

eval

  eval [arguments] 

The arguments are concatenated together into a single command, which is then read and executed, and its exit status returned as the exit status of eval. If there are no arguments or only empty arguments, the return status is zero.

Answer 2

$ ls | sed ... | source /dev/stdin

UPDATE: This works in bash 4.0, as well as tcsh, and dash (if you change source to . ). Apparently this was buggy in bash 3.2. From the bash 4.0 release notes :

Fixed a bug that caused `.' to fail to read and execute commands from non-regular files such as devices or named pipes.

Answer 3

Wow, I know this is an old question, but I've found myself with the same exact problem recently (that's how I got here).

Anyway - I don't like the source /dev/stdin answer, but I think I found a better one. It's deceptively simple actually:

echo ls -la | xargs xargs

Nice, right? Actually, this still doesn't do what you want, because if you have multiple lines it will concat them into a single command instead of running each command separately. So the solution I found is:

ls | ... | xargs -L 1 xargs

the -L 1 option means you use (at most) 1 line per command execution. Note: if your line ends with a trailing space, it will be concatenated with the next line! So make sure each line ends with a non-space.

Finally, you can do

ls | ... | xargs -L 1 xargs -t

to see what commands are executed (-t is verbose).

Hope someone reads this!

Answer 4

尝试使用进程替换 ，它将命令的输出替换为可以获取的临时文件：

source <(echo id)

Answer 5

I believe this is "the right answer" to the question:

ls | sed ... | while read line; do $line; done

That is, one can pipe into a while loop; the read command command takes one line from its stdin and assigns it to the variable $line . $line then becomes the command executed within the loop; and it continues until there are no further lines in its input.

This still won't work with some control structures (like another loop), but it fits the bill in this case.

Answer 6

`ls | sed ...`

I sort of feel like ls | sed ... | source - ls | sed ... | source - ls | sed ... | source - would be prettier, but unfortunately source doesn't understand - to mean stdin .

Answer 7

I think your solution is command substitution with backticks: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_04.html

See section 3.4.5

Answer 8

为什么不使用source呢？

$ ls | sed ... > out.sh ; source out.sh

Answer 9

要在bash 3.2（macos）上使用mark4o的解决方案，可以使用here字符串代替管道，如下例所示：

. /dev/stdin <<< "$(grep '^alias' ~/.profile)"