UNIX for Dummies Questions & Answers

I think it echoes "callversion.sh" because you source (using the .) version.sh. Make it executable and run it, then the echo will be "version.sh"

Hi Ariean,
I believe that DGPickett has already answered your questions. I'll go into a little more detail here since it is clear that you are a programming novice.

1) In the command line:

Code:

for i in "$TGT_DIR/$FILENAME"*.xml

the "$TGT_DIR/$FILENAME"*.xml will expand to a list of all of the files in the directory named by the expansion of "$TGT_DIR and $FILENAME. For purposes of this discussion, assume that $TGT_DIR expands to /dir and $FILENAME expands to ACC. If there are no matching files in that directory, the expansion of that filename matching pattern (and the value stored in the shell variable i the 1st (and only) time through the for loop) will be the string /dir/ACC*.xml. Then the test command:

Code:

[ "$i" != "${i#*[*]}" ]

will return TRUE (exit status 0) if the expansion of i is not the same as the expansion of i with the shortest string of any number of any characters and an asterisk character removed from the start of the expansion of i. So, in this case /dir/ACC*.xml will not be the same as .xml because there was an asterisk (*) in $i. Again, in this case, "${i#**}" (which expands to an empty string) is VERY different from "${i#*[*]}" (which expands to .xml). As DGPickett said, in a filename pattern matching expression, * is a metacharacter when it is not between square brackets. In this case it matches zero or more of any character. Inside square brackets[*], it only matches the asterisk itself.

In the more common case where at least one file matches the pattern, the value stored in i will not contain an asterisk.

2) The constructs:

Code:

        [ "$VER_NUM" -gt "$MAX_V" ] && MAX_V=$VER_NUM

and

Code:

        if [ "$VER_NUM" -gt "$MAX_V" ]
        then    MAX_V=$VER_NUM
        fi

are equivalent. You should be aware of both forms although I would never suggest that it would be wrong to always use the if, then, fi version. When there are imbedded comments in the then portion of an if, as there were in an earlier if statement in that for loop, you have to be very careful not to accidentally comment out the code you want to run as well when you use the first form above.

Use whichever form is easiest for you to understand.

3) In standards conforming shells, $0 expands to the pathname the shell used to invoke this script. If your script is named version.sh, then $0 could expand to something like version.sh, ./version.sh, or /home/ariean/bin/version.sh. The assignment IAM={0##*/} (similar to the "${i#*[*]}" above) removes the longest (because it uses ## instead of #) string on any number of characters ending with a "/" from the start of the contents of $0. So, for all of the possible values of $0 shown above, ${0##*/} expands to version.sh.

With both ${var#pattern} and ${var##pattern}, var will be expanded unchanged if the given pattern does not fully match a string at the start of the contents of var.

4) I don't have anything to add to what DGPickett already said here.

I see that you have posted another question while I've been working on this response. It looks like DGPickett and RudiC have already made great suggestions about how to get the correct name in your diagnostic messages.