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Re: Bash true/false builtings undocumented? "false" not working?

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On Fri, Aug 17, 2018 at 06:46:54PM +1000, Zenaan Harkness wrote:
> $ test $? && echo ok || echo error $?

Others have already pointed out that  test $?  is not what you think it
is.  When the test command is given 1 argument, it tests that argument's
string length.  If the string length is 0, then it's false.  If the
string length is non-zero, then it's true.

The string length of $? is always non-zero, so  test $?  is always true.

But what I really wanted to point out is that the  x && y || z  construct
is BROKEN and WRONG.  See <https://mywiki.wooledge.org/BashPitfalls#pf22>
for the verbose explanation.


On Fri, Aug 17, 2018 at 07:29:47PM +1000, Zenaan Harkness wrote:
> Is there a "cleaner" way to test the true/ error exit status other
> than using "$?", with bonus points for working in posix sh as well as
> Bash, ?

Simply use "if" like you're supposed to.

if mycommand arg1 arg2; then
  echo "it worked"
else
  echo "it failed"
fi

Or, if you only care about one of the two cases, you may use EITHER
the && or the || operator.  Just never, ever use both of them in the
same compound command.

mycommand arg1 arg2 || die "whoopsie"

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Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-17 10:50 +0200
  Re: Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-17 11:00 +0200
  Re: Bash true/false builtings undocumented? "false" not working? Nicolas George <george@nsup.org> - 2018-08-17 11:00 +0200
    Re: Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-17 11:30 +0200
    Re: Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-17 11:40 +0200
      Re: Bash true/false builtings undocumented? "false" not working? Nicolas George <george@nsup.org> - 2018-08-17 11:40 +0200
      Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-17 12:20 +0200
      Re: Re: Bash true/false builtings undocumented? "false" not working? Clive Standbridge <list-user@tgstandbridges.plus.com> - 2018-08-17 14:10 +0200
        Re: Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-17 15:40 +0200
      Re: Bash true/false builtings undocumented? "false" not working? Greg Wooledge <wooledg@eeg.ccf.org> - 2018-08-17 14:30 +0200
        Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-17 15:50 +0200
          Re: Bash true/false builtings undocumented? "false" not working? Greg Wooledge <wooledg@eeg.ccf.org> - 2018-08-17 16:20 +0200
            Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-17 16:40 +0200
              Re: Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-18 01:10 +0200
        Re: Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-18 01:30 +0200
  Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-17 11:30 +0200
    Re: Bash true/false builtings undocumented? "false" not working? Zenaan Harkness <zenaan@freedbms.net> - 2018-08-17 11:40 +0200
      Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-17 11:50 +0200
        Re: Bash true/false builtings undocumented? "false" not working? tomas@tuxteam.de - 2018-08-17 12:00 +0200
      Re: Bash true/false builtings undocumented? "false" not working? Stefan Krusche <linux@stefan-krusche.de> - 2018-08-23 15:00 +0200
        Re: Bash true/false builtings undocumented? "false" not working? <tomas@tuxteam.de> - 2018-08-23 16:30 +0200

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