The best way to explain this is with an example:
You may want to write a simple script that launches an xterm window with different color
options. Pseudo hash tables in bourne shell.
$ xwindow MidnightBlue
An easy way to this is by first listing the supported colors in the script (pseudo hash table):
DarkSlateGrey="#2f4f4f"
DimGrey="#696969"
MidnightBlue="#191970"
NavyBlue="#000080"
Next, simply grab the hex color code by using the following command:
BGColor=`eval echo $"$(echo $1)"`
"$(echo $1)" evaluates to "MidnightBlue" and
`eval echo $MidnightBlue evaluates to "#191970".
Simply launch the xterm window using $BGColor as the background color:
xterm -bg="$BGColor" &
This method for extracting pseudo hash values may be used for NIS map files, file date stamps, GUI colors, etc.
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1 comment:
This was really helpful, but sh can be pretty persnickety about the syntax here. I found that
value=`eval echo "\\$$(echo $key)"`
works better for reading a value.
changing a value is simple:
eval `echo $key`="newvalue"
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