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UNIX shell scripting


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hi there, having a bit of trouble with something in a shell script, i wonder if you could help me, im using the bourne shell...

i have a script which works on a file, but i want to make sure the user hasnt entered a pathname using an if statement, i assume theres a way to use regex here, but i cant seem to get it to work...

if [ $file = ***Not sure what to enter*** ]

then echo "$file: can't be a pathname"

when using awk i know you have to use a tilde rather than an = when using regular expressions and if statements, but that doesnt work here...

thanks for your help, and if anyone has any questions of a similar nature, here would probably be a reasonable place to ask them...

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  • 1 month later...

You could do something like this. . .

if [[ $file == */]]; then

  echo whatever


Then again, this will only check for a string ending with a '/'.

What if the user enters '/etc' or '/usr/bin' for example?

I'm sure you can figure out how to modify the example to check for these as well.

BTW, you should check out the Advanced Bash-Scripting Guide hxxp: tldp. org/LDP/abs/html/

it also has a section on Regular Expressions.


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-e = exists

-x = exists and is accessible

-d = exists and is a directory

-f = exists and is a file

Remember that '[' is actually a program (part of coreutils on Linux) so you need to have a space between it and whatever comes next.

Good: if [ -x "file.txt" ] ; then echo YES; fi

Bad: if [-x "file.txt" ] ; then echo YES; fi

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