1# $NetBSD: cmdline-redirect-stdin.mk,v 1.1 2021/02/01 20:31:41 rillig Exp $
2#
3# Demonstrate that the '!=' assignment operator can read individual lines
4# from make's stdin.
5#
6# This edge case is an implementation detail that has no practical
7# application.
8
9all: .PHONY
10	@printf '%s\n' "first line" "second line" \
11	| ${MAKE} -f ${MAKEFILE} read-lines
12
13.if make(read-lines)
14line1!=		read line; echo "$$line"
15line2!=		read line; echo "$$line"
16
17.if ${line1} != "first line"
18.  error line1="${line1}"
19
20.elif ${line2} == ""
21# If this branch is ever reached, the shell from the assignment to line1
22# probably buffers its input.  Most shells use unbuffered stdin, and this
23# is actually specified by POSIX, which says that "The read utility shall
24# read a single line from standard input".  This is the reason why the shell
25# reads its input byte by byte, which makes it terribly slow for practical
26# applications.
27.  error The shell's read command does not read a single line.
28
29.elif ${line2} != "second line"
30.  error line2="${line2}"
31.endif
32
33read-lines: .PHONY
34.endif
35