Can I use ECHO to execute commands?

Question

I've come up with a cool script that will produce the output that I need, but it only displays on the screen, so I have to copy, then paste in the commands to get them to execute. Here's the abbreviated version of my script:

#!/bin/bash
runc=/etc/csf/csf.pl -d
for IP in `tail -400 iptext.txt`
do
cc=`geoiplookup $IP`
echo -e $runc $IP    $cc | grep Algeria
echo -e $runc $IP    $cc | grep Argentina
echo -e $runc $IP    $cc | grep Armenia
echo -e $runc $IP    $cc | grep Azerbaijan
echo -e $runc $IP    $cc | grep Bolivia
echo -e $runc $IP    $cc | grep Brazil
done

Okay, so it loops through the list of IP addresses in iptext.txt, then does a geoIP lookup on each, if (in this example) there are two geoIP matches in the list, let's say for Armenia and Brazil, I will see output like this to the shell window:

/etc/csf/csf.pl -d 46.162.242.17 GeoIP Country Edition: AM, Armenia
/etc/csf/csf.pl -d 200.147.38.50 GeoIP Country Edition: BR, Brazil

This is great, but I want more than just output, I actually want the /etc/csf/csf.pl -d command to run, and block (just and only) the IP in the lines that match the country name, in the list.

I've tried various things with my limited knowledge of shell scripting, but so far, nothing seems to work. So is there some option for ECHO I am missing that would actually run the command rather than just printing out the line?

I have rollback your inclusion of an answer in the question itself. Please post your own answer or approve one of the existing one. Note that your solution was almost identical to Flo Doe's answer. — Cœur, Jan 24 '18 at 03:03

score 46 · Answer 1 · edited Oct 24 '18 at 18:43

46

Just put your command into parenthesis like this:

echo $(ls)

You can also have text before the command

echo "The date is $(date)"

For Example

echo "Enter Text Here $(Command Here)"

edited Oct 24 '18 at 18:43

Community

1
1

answered Jul 29 '17 at 13:32

Neeraj Verma

703
6
15

hek2mgl · Answer 2 · 2013-07-16T10:37:05.140

25

A simple way that won't need modification of your script would be to pipe the command's output to another bash instance. Like this:

yourscript | bash -

The - tells bash that it should read commands from stdin.

However, if you are not searching for a quick solution, it is possible to build and execute the command dynamically as well. Like this:

cmd="ls"
if [ "foo" != "bar" ] ; then
    cmd="$cmd -a"
then

# ... and so on

# now execute it:
$cmd

edited Jul 16 '13 at 10:37

answered Jul 16 '13 at 10:30

hek2mgl

152,036
28
249
266

1

You could also pipe the `for` loop into `bash`: `for x in ...; do ...; done | bash -` – glenn jackman Jul 16 '13 at 12:24
@glennjackman I wasn't sure and too lazy to test ;) ... piping the output of the loop sounds like the best solution to me. thx – hek2mgl Jul 16 '13 at 12:33

score 14 · Answer 3 · answered Jul 16 '13 at 10:38

14

You can use eval to execute a string:

eval $cmdstring

answered Jul 16 '13 at 10:38

Syntax

159
6

score 10 · Answer 4 · answered Jul 16 '13 at 10:41

There is a bash builtin eval, this executes commands like they were typed in at your shell. For example within your script you can do the following:

eval $(echo -e $runc $IP    $cc | grep Algeria)

This will process your echo in a subshell and the output will be executed like you typed it in your shell followed by enter.

See below exerpt from bash manual:

eval [arg ...] The args are read and concatenated together into a single command. This command is then read and executed by the shell, and its exit status is returned as the value of eval. If there are no args, or only null arguments, eval returns 0.

score 7 · Answer 5 · answered Mar 16 '17 at 18:00

7

echo `pwd`

above command works for me.

answered Mar 16 '17 at 18:00

Bobo

8,777
18
66
85

score 0 · Answer 6 · answered Jul 16 '13 at 10:41

Use grep -E and a pattern instead:

$runc $IP    $cc | grep -E 'Algeria|Argentina|...'

Explanation: echo will print the command but not execute it. Just omit it to actually execute the command.

And instead of running the script 5 times, use grep to search for any of the five patterns at once.

And you should use

cc=$(geoiplookup $IP)

instead of backticks; it's safer.

Can I use ECHO to execute commands?

6 Answers6