Checking for the file existence from the command line...

[dre2xl]

This is a DUMB question but the Google results were very busy... all scripting-related.

1) What's a simple way of determining if a file exists? find/slocate will print out multiple results if they exist. I just want a 'yes' or 'no' type response.

While I'm at it...
2) What's the best way to pipe output to grep as a file command argument (or any other commands for that matter)? For example, cat file_list | grep 'foo' will print out the lines of files that contain 'foo'... but what if I want to specify the lines themselves as file-name arguments to grep?

[Cabhan]

1) If you're using Bash or Perl, you can use the "-e" check to see if the file exists:

Bash:

file=/foo/bar

if [-e "$file"]; then
echo "Yay!"
fi

Perl:

$file = "/foo/bar";
print "Yay!" if -e $file;

2) I would do this in Perl as such:

open FILE, "/foo/bar";

chomp&#40;@lines = <FILE>&#41;;

for $file &#40;@lines&#41;
&#123;
    system "grep 'foo' $file";
&#125;

Basically, open the file, read it into an array, and use a foreach loop to feed each one into grep.

[CodeRoot]

1) ls <file specification>

2) grep 'something' `cat file_list | grep 'foo'`

[dre2xl]

Hey, the backquotes were exactly what I was looking for. Thanks!

[CodeRoot]

"You are welcome..."

[scm]

Hey, the backquotes were exactly what I was looking for. Thanks!

I think using $(command) is preferrable to backticks - they're a lot easier to nest for one thing! And less easy to inadvertently use the wrong quotes, too.

grep 'something' $(cat file_list | grep 'foo')`

[anomie]

What's a simple way of determining if a file exists? find/slocate will print out multiple results if they exist. I just want a 'yes' or 'no' type response.

file /path/to/file_here

Also gives you metadata about the file if it does exist.

[bryansmith]

If you are just looking in a specific directory, try

slocate <filename> | grep <dir>

after updatedb.

Bryan