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Shell Programming and Scripting
Reading data into muti-dimentional array - in perl
Post 50836 by cbkihong on Monday 3rd of May 2004 08:55:27 PM
05-03-2004
I decided to unveil the trap.
Without the "my", the result I got (with the original script) was
4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7
(4 5 6 7 printed four times). Shouldn't get the first three lines printed at all because all four references saved into @multiarray point to the same symbol table entry, which always refers to the most recent anonymous list read (each assignment to @ar overwrites the previous entry). That explains why four consecutive 4 5 6 7 is resulted. The line read from file is correct but the output doesn't.
With @ar declared "my", it becomes a lexical array variable which gets expired on each loop iteration (so at the time the block ends its reference count drops to 1 -- the only reference left is the one saved in @multiarray). Assignment to @ar in the next iteration no longer affects the previous saved reference because it is now a different variable from the earlier @ar.
That's why I said the trap is a subtle one that is not obvious from the surface.
Without the "my", the result I got (with the original script) was
4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7
(4 5 6 7 printed four times). Shouldn't get the first three lines printed at all because all four references saved into @multiarray point to the same symbol table entry, which always refers to the most recent anonymous list read (each assignment to @ar overwrites the previous entry). That explains why four consecutive 4 5 6 7 is resulted. The line read from file is correct but the output doesn't.
With @ar declared "my", it becomes a lexical array variable which gets expired on each loop iteration (so at the time the block ends its reference count drops to 1 -- the only reference left is the one saved in @multiarray). Assignment to @ar in the next iteration no longer affects the previous saved reference because it is now a different variable from the earlier @ar.
That's why I said the trap is a subtle one that is not obvious from the surface.
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atf-sh [-s shell] -- interpreter for shell-based test programs SYNOPSIS
atf-sh script DESCRIPTION
atf-sh is an interpreter that runs the test program given in script after loading the atf-sh(3) library. atf-sh is not a real interpreter though: it is just a wrapper around the system-wide shell defined by ATF_SHELL. atf-sh executes the inter- preter, loads the atf-sh(3) library and then runs the script. You must consider atf-sh to be a POSIX shell by default and thus should not use any non-standard extensions. The following options are available: -s shell Specifies the shell to use instead of the value provided by ATF_SHELL. ENVIRONMENT
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