91 lines
2.6 KiB
Makefile
91 lines
2.6 KiB
Makefile
# $NetBSD: var-op-shell.mk,v 1.6 2022/01/10 20:32:29 rillig Exp $
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#
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# Tests for the != variable assignment operator, which runs its right-hand
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# side through the shell.
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# The variable OUTPUT gets the output from running the shell command.
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OUTPUT!= echo "success"'ful'
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.if ${OUTPUT} != "successful"
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. error
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.endif
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# Since 2014-08-20, the output of the shell command may be empty.
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#
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# On 1996-05-29, when the '!=' assignment operator and Cmd_Exec were added,
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# an empty output produced the error message "Couldn't read shell's output
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# for \"%s\"".
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#
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# The error message is still in Cmd_Exec but reserved for technical errors.
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# It may be possible to trigger the error message by killing the shell after
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# reading part of its output.
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OUTPUT!= true
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.if ${OUTPUT} != ""
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. error
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.endif
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# The output of a shell command that failed is processed nevertheless.
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# Unlike the other places that run external commands (expression modifier
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# '::!=', expression modifier ':!...!'), a failed command generates only a
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# warning, not an "error". These "errors" are ignored in default mode, for
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# compatibility, but not in lint mode (-dL).
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OUTPUT!= echo "failed"; false
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.if ${OUTPUT} != "failed"
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. error
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.endif
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# A command with empty output may fail as well.
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OUTPUT!= false
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.if ${OUTPUT} != ""
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. error
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.endif
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# In the output of the command, each newline is replaced with a space.
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# Except for the very last one, which is discarded.
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OUTPUT!= echo "line 1"; echo "line 2"
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.if ${OUTPUT} != "line 1 line 2"
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. error
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.endif
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# A failing command in the middle results in the exit status 0, which in the
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# end means that the whole sequence of commands succeeded.
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OUTPUT!= echo "before"; false; echo "after"
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.if ${OUTPUT} != "before after"
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. error
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.endif
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# This should result in a warning about "exited on a signal".
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# This used to be kill -14 (SIGALRM), but that stopped working on
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# Darwin18 after recent update.
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OUTPUT!= kill $$$$
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.if ${OUTPUT} != ""
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. error
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.endif
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# A nonexistent command produces a non-zero exit status.
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OUTPUT!= /bin/no/such/command
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.if ${OUTPUT} != ""
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. error
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.endif
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# The output from the shell's stderr is not captured, it just passes through.
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OUTPUT!= echo "stdout"; echo "stderr" 1>&2
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.if ${OUTPUT} != "stdout"
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. error
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.endif
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# The 8 dollar signs end up as 4 dollar signs when expanded. The shell sees
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# the command "echo '$$$$'". The 4 dollar signs are stored in OUTPUT, and
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# when that variable is expanded, they expand to 2 dollar signs.
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OUTPUT!= echo '$$$$$$$$'
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.if ${OUTPUT} != "\$\$"
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. error
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.endif
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# As a debugging aid, log the exact command that is run via the shell.
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.MAKEFLAGS: -dv
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OUTPUT!= echo '$$$$$$$$'
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.MAKEFLAGS: -d0
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all:
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