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20 lines
701 B
Markdown
20 lines
701 B
Markdown
# Check If The First Argument Is Given
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In a shell script, you may want to check if an argument was given. Each
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argument is referenced numerically with the `$` prefix, so the first argument
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is `$1`. To check if the first argument is given, you can use the `-z` check.
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```bash
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if [ -z "$1" ]
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then
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echo "The first argument is missing"
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exit 1
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fi
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```
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The `-z` checks if the argument is a zero-length string (so `""` or undefined
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will be true). If it is missing, then we echo out a message and exit the
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script. This is how I might fashion a script that requires the first argument.
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[source](https://stackoverflow.com/questions/6482377/check-existence-of-input-argument-in-a-bash-shell-script)
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