Shell Programming and Scripting

I have a program that runs like "cat f1 - f2 -", I need to write shell script to run the program whose standard input will be redirected from 2 files. I spend a whole day on it, but didn't figure out. Can someone help me out? Thanks!

not exactly sure what your requirement is, but it sounds like:

redirect standard in from 2 files _at the same time_ to a single process

that is done like this:

Code:

cat f1 f2|process

or this

Code:

process<cat f1 f2

'cat' concatenates the files, so this is nearly equivalent to the following:

Code:

process < f1
process < f2

Thanks for your reply. But it still does not work. It says "cat: No such file or directory".
My program command can run like this: "./a.out file1.txt - file2.txt -", when the parameter is a file name, it will read file content, otherwise, when the parameter is a hyphen, it will read from stdin(just like "cat file1 - file2 -"). I need write a test script to run this program, however, I don't know how to redirect two file for stdin. Anybody can help me? Thanks.

can you post your script?

the error means that one of the arguments you are passing to 'cat' is not a file, or doesn't exist on the path you've indicated--however without seeing how you are calling 'cat' in your script, I can only speculate.

the code you have is treating cat as a file name.

Code:

process<cat f1 f2

to use this method you will need to do it in two steps

Code:

cat f1 f2 >/tmp/foo
process</tmp/foo

I don't really understand the requirements so I am not sure how to provide a solution. Having parameters like <file1> <-> <file2> <-> just does not seem right. What is the end result you are looking for?

You cannot redirect from a command with <; the argument must be a file.

If your shell has process substitution, you can do:

Code:

process < <(cat f1 f2)

Or use a here document:

Code:

process <<.
$( cat f1 f2 )
.

good point cfa. thx.