1# $NetBSD: varmod-assign-shell.mk,v 1.8 2024/07/04 17:47:54 rillig Exp $ 2# 3# Tests for the variable modifier '::!=', which assigns the output of a shell 4# command to the variable, but only if the command exited successfully. This 5# is different from the other places that capture the output of an external 6# command (variable assignment operator '!=', expression modifier ':sh', 7# expression modifier ':!...!'), which also use the output when the shell 8# command fails or crashes. 9# 10# The variable modifier '::!=' and its close relatives have been around since 11# var.c 1.45 from 2000-06-01. 12# 13# Before 2020.08.25.21.16.53, the variable modifier '::!=' had a bug for 14# unsuccessful commands, it put the previous value of the variable into the 15# error message instead of the command that was executed. That's where the 16# counterintuitive error message 'make: "previous" returned non-zero status' 17# comes from. 18 19DIRECT= previous 20# expect+1: warning: Command "echo output; (exit 13)" exited with status 13 21DIRECT!= echo output; (exit 13) 22 23ASSIGNED= previous 24.MAKEFLAGS: -dv # to see the "Capturing" debug output 25# expect+1: warning: while evaluating variable "ASSIGNED" with value "previous": Command "echo output; (exit 13)" exited with status 13 26_:= ${ASSIGNED::!=echo output; ${:U(exit 13)}} 27.MAKEFLAGS: -d0 28 29all: 30 @echo DIRECT=${DIRECT:Q} 31 @echo ASSIGNED=${ASSIGNED:Q} 32