🚀 go-pugleaf

In article <8908231654.AA10031@dash.mitre.org> barratt@DASH.MITRE.ORG (Jeff Barratt) writes:
>Bash Version 1.02
>Problem:
> Improper action from parameter test. A parameter that doesn't exist
>causes exit from the shell, rather than executing the "action".
> Example on machine "dash". Parameter ZIP does not exist:
>
>dash$ : ${ZIP:?"No ZIP here"}
>	shell exits

Here is what happens for me with bash:

cwns1$ echo $SHLVL
2
cwns1$ bash
cwns1$ echo $SHLVL
3
cwns1$ ${ZIP:?"No ZIP here"}
No ZIP here
cwns1$ echo $SHLVL
2

This is what happens with a S5r2 sh:

cwns1$ echo ${Z:?no}
Z: no
cwns1$ echo ${Z:?}
Z: parameter null or not set
cwns1$

This is what the spec mandates, and this behavior has been in the Bourne 
shell since its creation (i.e. 7th Edition).  Quoting from a random System
5 release 2+ man page (this happens to be from Ultrix 3.0 sh5):

${parameter:?word}
          If parameter is set and is non-null, substitute its
          value; otherwise, print word and exit from the shell.
          If word is omitted, the message ``parameter null or not
          set'' is printed.

The wording is essentially the same for the 4.3BSD sh, which means it was in
the 7th Edition sh.

I think it's brain-dead, but then I wasn't on the committee...

Chet Ramey
Chet Ramey			"We are preparing to think about contemplating 
Network Services Group, CWRU	 preliminary work on plans to develop a
chet@cwjcc.INS.CWRU.Edu		 schedule for producing the 10th Edition of 
				 the Unix Programmers Manual." -- Andrew Hume