Cron displaying error despite bash script running fine manually (Linux)

Question

So, I'm working on a bash script on a Linux VM for a class that pings multiple ip addresses from an input file and emails myself if there is any errors, while sending the results (successful or failed) to an output log. To get full credit we need to have it run every 5 minutes using cron. If I run it manually with the bash command, it works fine, doing all of the things it is supposed to do, but when it runs with cron I receive this error:

/home/kali/Documents/GitHub/BFOR206/hw1.sh: line 33: hw1_input.txt: No such file or directory

Here is my code:

#!/bin/bash

# File path for input (ip addresses)
hw1_input="~/Documents/GitHub/BFOR206/hw1_input.txt"

# Loop through and read each address in the file
while read -r address; do

# Ping the address and save the output
        ping -c 1 $address > /dev/null

# Check if ping was normal or failed
if [ $? -eq 0 ]; then

# If the ping is normal, log to a file
    echo "Ping successful for $address at $(date)" >> hw1_output.log
else

# If the ping failed. log the error to a file
    echo "Ping failed for $address at $(date)" >> hw1_output.log

# Send an email notification to self about error
    echo "Ping failed for $address at $(date)" | mail -s "Ping Error!" kali@kali
  fi
done < "hw1_input.txt"

The error is from the last line.

I'm very new to scripting so if anyone has any ideas of ways I can try and fix this, please try and explain it in simple terms. I've spent countless hours already trying to troubleshoot it myself so posting here is kind of my last resort.

If it helps, this is the script I am using to run the cron:

*/5 *  *   *   *     bash ~/Documents/GitHub/BFOR206/hw1.sh

Change `done < "hw1_input.txt"` to `done < "$hw1_input"`. You're missing the directory path to the file. Isn't that why you set the variable in the first place? — Barmar, Mar 07 '23 at 00:59

score 0 · Accepted Answer · answered Mar 07 '23 at 01:03

Two problems:

Quoting the pathname prevents bash from expanding ~ into your home directory. Don't quote in the assignment to hw1_input.
You don't have the directory path in the filename you're redirecting from. You should use the hw1_input variable.

#!/bin/bash

# File path for input (ip addresses)
hw1_input=~/Documents/GitHub/BFOR206/hw1_input.txt

# Loop through and read each address in the file
while read -r address; do
    # Ping the address and save the output
    ping -c 1 $address > /dev/null
    
    # Check if ping was normal or failed
    if [ $? -eq 0 ]; then    
        # If the ping is normal, log to a file
        echo "Ping successful for $address at $(date)" >> hw1_output.log
    else
        # If the ping failed. log the error to a file
        echo "Ping failed for $address at $(date)" >> hw1_output.log
        # Send an email notification to self about error
        echo "Ping failed for $address at $(date)" | mail -s "Ping Error!" kali@kali
    fi
done < "$hw1_input"

I'd also recommend using `if ping...` rather than testing `$?` afterward; see ["Why is testing $? to see if a command succeeded or not, an anti-pattern?"](https://stackoverflow.com/questions/36313216/why-is-testing-to-see-if-a-command-succeeded-or-not-an-anti-pattern) — Gordon Davisson, Mar 07 '23 at 05:11

Cron displaying error despite bash script running fine manually (Linux)

1 Answers1