Dynamically choosing the interpreter


 
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# 1  
Old 04-16-2012
Dynamically choosing the interpreter

Hi,

Is it possible to choose the inerpreter conditionally.
For example, if
Code:
whereis bash

returns
Code:
/usr/bin/bash

then i need to choose
Code:
#!/usr/bin/bash

else i need to use
Code:
#!/usr/bin/sh

.

Is it possible to achieve in a shell script?

Thanks
# 2  
Old 04-16-2012
That's not possible, I'm afraid, you can use /usr/bin/env as shebang to find the user's preferred command, or rather, the command in the user's environment. But you can't "change" the shebang dynamically.

I'd go for something like this
Code:
#!/usr/bin/env sh

mybash=$(command -v bash 2>/dev/null)
## maybe switch to bash
if test "${0}" != "bash" -a -n "${mybash}"; then
  exec command bash $0 $@
fi

or something along the lines of that.
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