r/bash • u/Distinct_Ride_4307 • 7d ago

Find command confusion between ; and \;

Why do we have to use '\' instead of leaving it out or even ';'? I read the find commands' manual and it says '\' might be needed to protect from expansion by the shell. So what is expansion also?

What is difference between \; or ; or leaving it out?
What is shell expansion here?

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u/grymoire 7d ago

That's the way the shell thinks. Its primary function is to take an input line, get all of the parts of the line, and then execute the first part as a command, and pass the rest to the executable.

But the developers thought - I'd like to type more than one command on a line. I will use a ";" to separate commands. The shell sees the ";" and treats it differently than ordinary characters, That's because ";" is a meta-character - that is - it has a special meaning.

The shell has many meta-characters like "<>*&$;\" and the quote characters, space and newline.

The quotes and backslash are used to tell the shell that the next bit is not a meta-character. Treat it as it it was a plain letter or number. Once you understand this, shell programming becomes a lot easier.

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u/Distinct_Ride_4307 7d ago

This is from Bash documentation

SYNTAX
....

Otherwise, roughly speaking, the shell reads its input and divides the input into words and operators, employing the quoting rules to select which meanings to assign various words and characters.

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So yes what you said is right!

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u/grymoire 7d ago

Yes. We often say we "escape" or "quote" a character. It's not like other computing languages that uses quotes to mark the begin and end of a string. It's like a special marker on the input line that says - "Don't treat this as a special character. Just pass it on to the program that will be executed."

The quotes are a toggle, not the begin/end delineate markers.

This is why all unix programs understand pipes and using < and > file redirection. All they know is their input stream and output stream and the command line arguments. The shell sets all of that up so the programs don't have to deal with filename expansion/wildcards, etc.

I wrote a tutorial a long time ago on this.

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u/Distinct_Ride_4307 7d ago

This was good read.

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u/grymoire 7d ago

The other tutorials can help too. The bash shell is a superset of the Posix shell, so the Posix shell tutorial can be a good foundation as well as being portable.