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35 lines
1.8 KiB
35 lines
1.8 KiB
2 years ago
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#!/bin/sh
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# To make this script executable, use the command: chmod +x 09_debugging.sh
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# To run the script, use the command: ./09_debugging.sh
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echo "This spell will teach you the basics of script debugging and error handling in POSIX-compliant Bash"
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echo "To study the code of the examples, please use the command: cat 09_debugging.sh"
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# echo and set -x (debugging)
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echo "The echo command is used to print messages to the terminal. The set -x command enables the display of commands and their arguments as they are executed."
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echo "Example: set -x; echo 'Debugging message'; set +x"
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set -x; echo 'Debugging message'; set +x
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# trap and signal handling (error handling)
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echo "The trap command is used to catch signals sent to the script. Signals are used to communicate with processes, and are typically sent when a program needs to terminate or interrupt another program."
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echo "Example: trap 'echo Signal received, exiting...; exit 0' INT; sleep 10; echo 'This line will not be executed'"
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trap 'echo Signal received, exiting...; exit 0' INT; sleep 10; echo 'This line will not be executed'
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# exit status and return values (error handling)
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echo "Every command in Bash returns an exit status, which is the value that the command returns to the parent process. The value can be checked using the $? variable. A value of 0 indicates success, and any other value indicates failure."
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echo "Example: echo $? (this should be 0)"
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echo $?
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# Using the exit status in a conditional statement
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command
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if [ $? -eq 0 ]; then
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echo "Command executed successfully"
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else
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echo "Command failed with exit status $?"
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fi
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# Setting the exit status of the script
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echo "You can also set the exit value of a script manually with the 'exit' command. 0 means success, every other value is an error. This script will exit with an error code of 42."
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exit 42
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echo "Spell cast successfully"
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