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I was just wondering whether or not this script code would properly test for the existence of a dir2, and if it doesn't exist, then to create it. Dir1 already exists.

[ ! -d /dir1/dir2  ] && mkdir /dir1/dir2
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    No - not unless /dir1/ definitely already exists. Use mkdir -p /dir1/dir2 and forget the test. Commented Feb 20, 2015 at 6:47
  • ya, Dir1 already existed, it was the end of the path of my home directory. We had to run it as a test, I didn't get the extra credit for it and was wondering if it was incorrect. Thank you. Commented Feb 20, 2015 at 6:55
  • mkdir -p will fail as well if dir2 exists as a file other than a directory - or if permissions forbid you to create dirs for whatever reason. I usually do like mkdir -p ./target/dir && cd ./target/dir || exit Commented Feb 20, 2015 at 7:06
  • Assuming there exists no issues with permissions,and that dir2 doesn't already exist as a file, my test will work, correct? I can't run to check atm. Commented Feb 20, 2015 at 7:10
  • I'm not using mkdir -p. Dir1 already exists, i'm testing to see if dir2 exists as a subdirectory of dir1, and to create it only if it doesn't exist. Why would I need to test for dir1 as well? Commented Feb 20, 2015 at 7:18

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Your command can fail if dir1/dir2 exists but is not a directory. If you want to test whether dir1/dir2 exists at all, use -e

[ -e dir1/dir2 ] || mkdir dir1/dir2

If you really need dir1/dir2 to be a directory, and an ordinary file with that name is an error and should be replaced, you can test for that case.

[ -e dir1/dir2 ] && [ ! -d dir1/dir2 ] && rm dir1/dir2
[ -d dir1/dir2 ] || mkdir dir1/dir2
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  • I've added some more text explaining when that's appropriate Commented Feb 20, 2015 at 7:50
  • dir1/dir2 already exists, it doesn't exist in any other fashion than being a directory. Since this is the case, I should be in good shape? This was asked of me as extra credit is the only reason I'm doing it in this manner. I see that -d option is for "file exists and is a directory" whereas -e option is for "file exists." Why wouldn't -d be a better choice, as it is testing to confirm that it is a directory not only a file? Also, thanx for the additional info, will come in handy in the future! This is my first script, so I apologize for the stubbornness. Commented Feb 20, 2015 at 7:55
  • There's no need to test that it's a directory if it's guaranteed to be a directory if it exists. Commented Feb 20, 2015 at 8:01
  • And that is the reasoning for using the -e option? Commented Feb 20, 2015 at 8:04
  • Yes. You only need to check whether it already exists. You don't need to test whether it's a directory, because you know it will be. Just like you don't need to test whether dir1 exists, because you know it does. Commented Feb 20, 2015 at 8:06

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