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Chunks of bash shell programming


 
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# 8  
Old 09-22-2013
Quote:
Originally Posted by lg123
Code:
A=${0##*/}
S=${0%/*}

Please explain me with examples for the above 2 statements.]
The shell sets $0 to the name used to invoke the script that is running. So, if you script is named test.sh and it is located in the directory /home/user/bin, $0 could expand to test.sh, ./test.sh, /home/user/bin/test.sh, or several other possibilities.

${variable##pattern} will expand to the value of $variable with the longest string matching the pattern pattern removed from the beginning of the string. If pattern doesn't match anything at the start of the string, the result is the same as the expansion of ${variable}. So if $0 expands to test.sh, ./test.sh, or /home/user/bin/test.sh; ${0##*/} will expand to test.sh.

Similarly, ${variable%pattern} expands to the expansion of $variable with the shortest match for pattern removed from the end. So, for the same values of $0 above, ${0%/*} will expand to test.sh, ., and /home/usr/bin, respectively.

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