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From: Seb <sbb@tuxfamily.org>
To: "Марк Коренберг" <socketpair@gmail.com>
Cc: dash@vger.kernel.org
Subject: Re: exec command and error checking
Date: Tue, 28 Jan 2014 14:40:56 +0100	[thread overview]
Message-ID: <20140128144056.ac2c1804a662b66678acfdab@tuxfamily.org> (raw)
In-Reply-To: <CAEmTpZGqBfdBQDnmw-TozGTXpUxShCC=rWObhaP4zmKFJu4jUw@mail.gmail.com>

Le Tue, 28 Jan 2014 18:16:23 +0600
Марк Коренберг a écrit:

> $ exec 9<no_such_file && echo TEST
> dash: 1: cannot open no_such_file: No such file

As previously said, POSIX specifies that the built-in redirection
errors cause the shell to exit. See:

  http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_20
  http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_08_01
  
> $ exec 9<no_such_file || echo TEST
> dash: 2: cannot open no_such_file: No such file
> 
> So, I cannot test this operation without using $?

You can use the file tests:

 if [ -f no_such_file -a -r no_such_file ]; then
   exec 9<no_such_file
 else
   echo TEST
 fi

or a subshell:

 if ( exec 9<no_such_file ) 2>/dev/null; then
   exec 9<no_such_file
 else
   echo TEST
 fi

++
Seb.

  parent reply	other threads:[~2014-01-28 13:41 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-28 12:16 exec command and error checking Марк Коренберг
2014-01-28 13:17 ` Guido Berhoerster
2014-01-28 15:32   ` Paul Gilmartin
2014-01-28 21:59   ` Jilles Tjoelker
2014-01-28 23:18     ` Guido Berhoerster
2014-01-29  3:19     ` Chet Ramey
2014-01-28 13:40 ` Seb [this message]
2014-01-28 14:05   ` Guido Berhoerster
2014-01-28 14:42     ` Seb
2014-01-28 14:52 ` Paul Gilmartin

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