read stdin in function in bash script

问题:

I have some set of bash functions which output some information:

• find-modelname-in-epson-ppds
• find-modelname-in-samsung-ppds
• find-modelname-in-hp-ppds
• etc ...

I've been writing functions which read output and filter it:

function filter-epson {
    find-modelname-in-epson-ppds | sed <bla-blah-blah>
}

function filter-hp {
    find-modelname-in-hp-ppds | sed <the same bla-blah-blah>
}
etc ...

But the I thought that it would be better do something like this:

function filter-general {
    (somehow get input) | sed <bla-blah-blah>
}

and then call in another high-level functions:

function high-level-func {
    # outputs filtered information
    find-modelname-in-hp/epson/...-ppds | filter-general 
}

How can I achieve that with the best bash practices?

回答1:

If the question is How do I pass stdin to a bash function?, then the answer is:

Shellscript functions take stdin the ordinary way, as if they were commands or programs. :)

input.txt:

HELLO WORLD
HELLO BOB
NO MATCH

test.sh:

#!/bin/sh

myfunction() {
    grep HELLO
}

cat input.txt | myfunction

Output:

hobbes@metalbaby:~/scratch$ ./test.sh 
 HELLO WORLD 
 HELLO BOB 

Note that command line arguments are ALSO handled in the ordinary way, like this:

test2.sh:

#!/bin/sh

myfunction() {
    grep "$1"
}

cat input.txt | myfunction BOB

Output:

hobbes@metalbaby:~/scratch/$ ./test2.sh 
 HELLO BOB 

回答2:

To be painfully explicit that I'm piping from stdin, I sometimes write

cat - | ...

回答3:

Call sed directly. That's it.

function filter-general {
    sed <bla-blah-blah>
}