Safely parsing parameters


 
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# 15  
Old 01-14-2012
Quote:
I have a string like

Code:
root=/dev/sda3 noacpi foo "Baz mumble"
Sorry to be a pedant, or just plain thick! My question in post #10 still applies, but I'll rephrase it.
How did we arrive at the situation in post #1. i.e. What code, parameters or whatever produced or defined "root". I can achieve the assignment with backslashes but I just wondered whether is a free-standing command, a line from an parameter file or just (as I now suspect) a visual representation of what is in the environment variable without any syntax intended.

I have had a similar problem when writing a script to search thousands of alien scripts written to no particular standard. It was important that the search process never executed arbitary code.

Last edited by methyl; 01-14-2012 at 12:24 PM..
# 16  
Old 01-16-2012
Quote:
Originally Posted by methyl
Sorry to be a pedant, or just plain thick! My question in post #10 still applies, but I'll rephrase it.
How did we arrive at the situation in post #1. i.e. What code, parameters or whatever produced or defined "root".
A string saved in /boot/grub/grub.conf. Once the system boots, it gets read back out of the kernel via /proc/cmdline and processed by my bootloader, to decide which real root device should be used depending on the device ID string or the like.

In trying to find a safe way to process it I realized I'd happened upon a general class of problems that's difficult to tackle in shell -- processing quoting for strings which have somehow landed in the shell with real, actual quotes intact.

I'm pretty happy xargs can do it. Smilie

Last edited by Corona688; 01-16-2012 at 12:26 PM..
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