bash script to read commands from text file and abort if any command fails

hruday · 03-01-2017, 11:57 PM

I've bash script written to read each line of a file which has commands and execute them one by one.

#!/bin/bash

while read -r line
do
command ${line}
done< /root/ansi-pb/sample.txt

sample.txt has following commands

echo "hello world"
df -h
free -m
mkdir /tmp/`hostname`_bkp
touch /tmp/`hostname`_bkp/file{1..5}
mvn -version
echo "directory and files created"

Now if any command fails say mvn -version then script should stop executing next command.

How to achieve this?

pan64 · 03-02-2017, 01:42 AM

so add

Code:

#!/bin/bash
set -e

at the beginning of that sample.txt, make it executable and run.

ondoho · 03-02-2017, 02:35 AM

Code:

#!/bin/bash

while read -r line
do
$line || exit 1
done< /root/ansi-pb/sample.txt

hruday · 03-02-2017, 04:12 AM

Quote:

Originally Posted by ondoho

Code:

#!/bin/bash

while read -r line
do
$line || exit 1
done< /root/ansi-pb/sample.txt

Thank u,

I just want to improvise the script, so if I correct my command and run script again it should start executing from the command it got failed instead of executing from first command. Will it be possible in bash scripting.

pan64 · 03-02-2017, 04:49 AM

that is something called state-machine, you need to save the state at the time of failure and restart from there. Not really trivial....

rtmistler · 03-02-2017, 08:05 AM

Quote:

Originally Posted by hruday

Thank u,

I just want to improvise the script, so if I correct my command and run script again it should start executing from the command it got failed instead of executing from first command. Will it be possible in bash scripting.

Quote:

Originally Posted by pan64

that is something called state-machine, you need to save the state at the time of failure and restart from there. Not really trivial....

This is quite correct. You need to save the information, have your script stop and prompt, allow yourself to attempt to correct the TXT file and then use the prompt in your script to continue. Bear in mind that depending how you "remember" where you were, things may also change. For instance, say you remembered line number of the text file, and then you go and edit the text file and delete a ton of lines, thus changing it, you'll then change the circumstances by which you remembered where you were. As pan64 points out, this is not trivial.

Jjanel · 03-04-2017, 03:28 AM

Reminds me of 'doing' LFS book [not that I have]

Maybe add an incremental count [if $?==0]; echo $count >myStateFile
Then, as initialization, skip-read that many lines of the input file.

I think

Best wishes. Let 'us' know!

Shadow_7 · 03-06-2017, 04:56 AM

FILE: temp.txt

Code:

echo "hello world"
df -h
free -m
mkdir /tmp/`hostname`_bkp
touch /tmp/`hostname`_bkp/file{1..5}
mvn -version

FILE: temp.sh

Code:

#!/bin/bash
while read LINE
do
  if ( $LINE ) then
    echo -n $LINE" ... "
    echo "[ OK ]"
  else
    echo -n $LINE" ... "
    echo "[ FAILED ]"
    exit 1
  fi
done
echo "directory and files created"
exit 0

$ temp.sh < temp.txt

alternatively to have less output.

Code:

if ( ! $LINE ) then; exit 1; fi

Shadow_7 · 03-06-2017, 05:19 AM

Since a restart would be manual, you could have a counter and use "tail -n $REMAINING_COUNT $FILE" as the input. But always test first as there could be some inclusive / exclusive quirks depending on version of bash / tail / ... and the default environment of a given distro. Or manually edit the input to compensate for completed tasks for peace of mind. On a copy ofc, and remove it when done. But I cut my teeth on mainframes with single threaded batch processing. Step 1, create a list. Step 2, do the list. Step 3, verify. Step 4, if fail then cry.

pan64 · 03-06-2017, 05:25 AM

Quote:

Originally Posted by Shadow_7

Code:

if ( ! $LINE ) then; exit 1; fi

that is post #2

nodir · 03-06-2017, 06:45 AM

if ( ! "$LINE" ): And i am not sure why one would want a subshell at all. And use more quotes.