shell script - run list of commands

Question

for i in `cat foo.txt`
do
    $i
done

And I have a input file "foo.txt", with list of commands.

ls -ltr | tail
ps -ef | tail
mysql -e STATUS | grep "^Uptime"

when I run the shell script, it executes, but splits the commands in each line at spaces i.e for first line it executes only "ls", then "-ltr" for which I get command not found error.

How can I run each list as one command?

why am I doing this?

I execute lot of arbitrary shell commands including DB commands. I need to have a error handling as I execute each command(each line from foo.txt), I can't think of what can go wrong, so the idea is put all commands in order and call them in loop and check for error (#?) at each line and stop on error.

See @lasrks answer. Additionally, for i in `cat foo.txt` is a UUOc (Unnecessary Use Of cat) If you ever find yourself doing cat something and you are not concatenating something with another file -- it's likely a UUOc. Instead redirect your file to the loop, e.g. while read -r line; do ##stuff with line; done < foo.txt Do not eval $line to try and execute each line. eval is only once character away from evil. Source the file as the answer shows. — David C. Rankin
– David C. Rankin, Commented Dec 22, 2019 at 1:03

larsks · Accepted Answer · 2019-12-24 00:35:22Z

2

Why not just do this?

set -e
. ./foo.txt

set -e causes the shell script to abort if a command exits with a non-zero exit code, and . ./foo.txt executes commands from foo.txt in the current shell.

but I guess I can't send notification (email).

Sure you can. Just run the script in a subshell, and then respond to the result code:

#!/bin/sh

(
set -e
. ./foo.txt
)

if [ "$?" -ne 0 ]; then
  echo "The world is on fire!" | mail -s 'Doom is upon us' [email protected]
fi

edited Dec 24, 2019 at 0:35

answered Dec 22, 2019 at 0:55

larsks

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4 Comments

gvphubli.blogspot.com Over a year ago

This does stop on error - but I guess I can't send notification (email).

gvphubli.blogspot.com Over a year ago

@arsks - I tried your modified script, it does not stop on error, its does show "command not found error" I guess that is is raised by the subshell. I even tried adding "exit 1" after your echo statement in IF block. It does not stop it continues to next command in list.

larsks Over a year ago

This code works just fine (I even tested it!). If you're getting a "command not found" error you're making a basic mistake (e.g., not providing the correct path to a command).

gvphubli.blogspot.com Over a year ago

sorry - yes it does works, I did not notice that the error check does not have "exit" due to which it was continuing (after error), I just added "exit", so it stops on error.

Vishal · Accepted Answer · 2019-12-26 06:52:12Z

0

Code mentioned.

for i in `cat foo.txt`
do
    $i
done

Please use https://www.shellcheck.net/

This will result    _ 
    $ shellcheck myscript

Line 1:
for i in `cat foo.txt`
^-- SC2148: Tips depend on target shell and yours is unknown. Add a shebang.
         ^-- SC2013: To read lines rather than words, pipe/redirect to a 'while read'   loop.
         ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: (apply this, apply all SC2006)
for i in $(cat foo.txt)

$

Will try while loop, and for test purpose content of foo.txt mentioned below

cat foo.txt
    ls -l /tmp/test
    ABC
    pwd



 while read -r line; do $line; if [ "$?" -ne 0 ]; then echo "Send email Notification stating  $line Command reported error "; fi; done < foo.txt

 total 0
-rw-r--r--. 1 root root 0 Dec 24 11:41 test.txt
bash: ABC: command not found...
Send email Notification stating  ABC Command reported error
/tmp

In case error reported you can break the loop. http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_09_05.html

while read -r line; do $line; if [ "$?" -ne 0 ]; then echo "Send email Notification  stating  $line Command reported error "; break; fi; done < foo.txt

total 0
-rw-r--r--. 1 root root 0 Dec 24 11:41 test.txt
bash: ABC: command not found...
Send email Notification stating  ABC Command reported error




 while read -r line; do eval $line; if [ "$?" -ne 0 ]; then echo "Send email Notification stating  $line Command reported error "; break; fi; done < foo.txt
total 0
-rw-r--r--. 1 root root 0 Dec 24 11:41 test.txt
   bash: ABC: command not found...
Send email Notification stating  ABC Command reported error

edited Dec 26, 2019 at 6:52

answered Dec 24, 2019 at 6:19

Vishal

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2 Comments

gvphubli.blogspot.com Over a year ago

I tried your solution as well, I still see 2 issues. The commands are split at space eg: ls -ltr | tail will give error "ls: |: No such file or directory " and "ls: tail: No such file or directory" Its traps/shows error, but it continues to following line/command

Vishal Over a year ago

man7.org/linux/man-pages/man1/eval.1p.html In above code use eval while read -r line; do eval $line; if [ "$?" -ne 0 ]; then echo "Send email Notification stating $line Command reported error "; break; fi; done < foo.txt

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