« The first important observation about the crontab file is this: It’s not a shell script. Sure, it looks a bit like a shell script since you can set some variables, but it’s not. It’s best to think of the crontab as an interpreted file that happens to support some variable declarations that look a lot like a shell script. But they are simple name = value pairs NOT shell variables. The “value” must be a simple value. For example, you can not de-reference a crontab “variable” in a value

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#Does not work because sub-shells have no meaning in a crontab file.
PATH=`path_script`:/bin

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Percent signs need to be escaped »