1# $NetBSD: var-op-shell.mk,v 1.7 2023/06/01 20:56:35 rillig Exp $ 2# 3# Tests for the != variable assignment operator, which runs its right-hand 4# side through the shell. 5 6# The variable OUTPUT gets the output from running the shell command. 7OUTPUT!= echo "success"'ful' 8.if ${OUTPUT} != "successful" 9. error 10.endif 11 12# Since 2014-08-20, the output of the shell command may be empty. 13# 14# On 1996-05-29, when the '!=' assignment operator and Cmd_Exec were added, 15# an empty output produced the error message "Couldn't read shell's output 16# for \"%s\"". 17# 18# The error message is still in Cmd_Exec but reserved for technical errors. 19# It may be possible to trigger the error message by killing the shell after 20# reading part of its output. 21OUTPUT!= true 22.if ${OUTPUT} != "" 23. error 24.endif 25 26# The output of a shell command that failed is processed nevertheless. 27# Unlike the other places that run external commands (expression modifier 28# '::!=', expression modifier ':!...!'), a failed command generates only a 29# warning, not an "error". These "errors" are ignored in default mode, for 30# compatibility, but not in lint mode (-dL). 31# expect+1: warning: "echo "failed"; false" returned non-zero status 32OUTPUT!= echo "failed"; false 33.if ${OUTPUT} != "failed" 34. error 35.endif 36 37# A command with empty output may fail as well. 38# expect+1: warning: "false" returned non-zero status 39OUTPUT!= false 40.if ${OUTPUT} != "" 41. error 42.endif 43 44# In the output of the command, each newline is replaced with a space. 45# Except for the very last one, which is discarded. 46OUTPUT!= echo "line 1"; echo "line 2" 47.if ${OUTPUT} != "line 1 line 2" 48. error 49.endif 50 51# A failing command in the middle results in the exit status 0, which in the 52# end means that the whole sequence of commands succeeded. 53OUTPUT!= echo "before"; false; echo "after" 54.if ${OUTPUT} != "before after" 55. error 56.endif 57 58# This should result in a warning about "exited on a signal". 59# This used to be kill -14 (SIGALRM), but that stopped working on 60# Darwin18 after recent update. 61# expect+1: warning: "kill $$" exited on a signal 62OUTPUT!= kill $$$$ 63.if ${OUTPUT} != "" 64. error 65.endif 66 67# A nonexistent command produces a non-zero exit status. 68# expect+1: warning: "/bin/no/such/command" returned non-zero status 69OUTPUT!= /bin/no/such/command 70.if ${OUTPUT} != "" 71. error 72.endif 73 74# The output from the shell's stderr is not captured, it just passes through. 75OUTPUT!= echo "stdout"; echo "stderr" 1>&2 76.if ${OUTPUT} != "stdout" 77. error 78.endif 79 80# The 8 dollar signs end up as 4 dollar signs when expanded. The shell sees 81# the command "echo '$$$$'". The 4 dollar signs are stored in OUTPUT, and 82# when that variable is expanded, they expand to 2 dollar signs. 83OUTPUT!= echo '$$$$$$$$' 84.if ${OUTPUT} != "\$\$" 85. error 86.endif 87 88 89# As a debugging aid, log the exact command that is run via the shell. 90.MAKEFLAGS: -dv 91OUTPUT!= echo '$$$$$$$$' 92.MAKEFLAGS: -d0 93 94all: 95