bash script to iterate from middle of a list

Sai Ram Metla 0
Viewed 40

I have a bash script that iterates over a folder of sql scripts. I want it to run intelligently when the script encounters an error. I don't want to run a step twice.

for a in $files_list; do
 command 1
 command 2 
.
.
done

If 1,2,3,4,5 are the files to be executed and script exits at step 3 with some error. In next execution, I want to run from step 3 only. I have a variable in place for detecting at which step the script exited. I am stuck at starting the iteration from that variable. Is it something that can be done? Any suggestion is accepted. I'm open to change my logic as well.

sh shell bash loops
1 Answers

Didn't really spend much time but Let's say all the commands you want to execute are stored in a file test.txt

test.txt

ls
cal
du
d
date
ls

The following bash script takes two arguments filename where the commands are stored and the checkpoint from where it needs to start.

test.sh

## Function to read a file line by line

checkpoint=$2
filename=$1
checkpointReached=false

read_file_line_by_line() {
    local file="$1"
    while IFS= read -r line
    do
        if [ $checkpointReached == "false" ] && [ "$line" != "$checkpoint" ] ; then
            echo "...... Finding checkpoint....... current line is $line"
        fi
        if [ "$line" == "$checkpoint" ]; then
        echo "        *************************************************
                Checkpoint reached. Commands after checkpoint
        *****************************************************"        
            checkpointReached=true
            continue
        fi

        if $checkpointReached; then
            echo "        $line"
            execute_command $line
        fi
    done < "$file"
}

function execute_command() {
    local command="$1"
    echo "   Executing ..........     $command"
    if eval $command; then
        echo "   Command executed successfully"
    else
        echo "   Command failed. Exiting........"
        echo "   Please note the new checkpoint.... $command"
        exit 1
    fi
}

read_file_line_by_line "$filename"

Let's run it the first time, the checkpoint is the first command i.e. ls and its expected to fail at d which is invalid command

╰─ bash test.sh text.txt "ls"
        *************************************************
                Checkpoint reached. Commands after checkpoint
        *****************************************************
   Executing ..........     ls
test.sh         test.yaml       text.txt
   Command executed successfully
        du
   Executing ..........     du
24      .
   Command executed successfully
        d
   Executing ..........     d
test.sh: line 33: d: command not found
   Command failed. Exiting........
   Please note the new checkpoint.... d

Now we know the checkpoint. So we pass it along. Assuming that d is fixed now, we change it with echo for the sake of the script. In your case the script d would be fixed.

╰─ bash test.sh text.txt "echo"
...... Finding checkpoint....... current line is ls
...... Finding checkpoint....... current line is du
        *************************************************
                Checkpoint reached. Commands after checkpoint
        *****************************************************
   Executing ..........     echo

   Command executed successfully
        date
   Executing ..........     date
Mon Sep 12 14:50:44 +04 2022
   Command executed successfully

Let me know if this helps.

codeaprendiz0
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