Simulated Bourne Shell Functions and Aliases
If you have a Bourne shell with no functions () or aliases (), you can do a lot of the same things with shell variables and the eval () command.
Let's look at an example. First, here's a shell function named scp (safe copy). If the destination file exists and isn't empty, the function prints an error message instead of copying:
test |
scp() {
if test ! -s "$2" then cp "$1" "$2" else echo "scp: cannot copy $1: $2 exists" fi }
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If you use the same scp twice, the first time you'll make bfile. The second time you try, you see the error:
$scp afile bfile... $scp afile bfilescp: cannot copy afile: bfile exists
Here's the same scp-stored in a shell variable instead of a function:
scp=" if test ! -s "$2" then cp "$1" "$2" else echo "scp: cannot copy $1: $2 exists" fi "
Because this fake function uses shell parameters, you have to add an extra step: setting the parameters. Simpler functions are easier to use:
set |
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- JP