Why NonZero Exit Status
in [Shell]
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From: #! /shell/nerd on 15 Jan 2010 23:35 Hi, I have a function MyFunc() and it prints some stuff & always returns 0. In order to suppress it I'm redirecting STDOUT to NULL. Now when I try a. MyFunc >&- ExitStatus=$? I get the ExitStatus as 1. Where when I try b. MyFunc >/dev/null ExitStatus=$? I get the ExitStatus as 0. Why ??
From: Chris F.A. Johnson on 15 Jan 2010 23:40 On 2010-01-16, #! /shell/nerd wrote: > Hi, > > I have a function MyFunc() and it prints some stuff & always returns > 0. > In order to suppress it I'm redirecting STDOUT to NULL. Now when I try > > a. MyFunc >&- > ExitStatus=$? > I get the ExitStatus as 1. Where when I try > > b. MyFunc >/dev/null > ExitStatus=$? > I get the ExitStatus as 0. > Why ?? Did you not get an error messsage saying that you had a bad file descriptor? '>&-' is incorrect. -- Chris F.A. Johnson, author <http://shell.cfajohnson.com/> =================================================================== Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress) Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress) ===== My code in this post, if any, assumes the POSIX locale ===== ===== and is released under the GNU General Public Licence =====
From: #! /shell/nerd on 15 Jan 2010 23:41 On Jan 15, 10:40 pm, "Chris F.A. Johnson" <cfajohn...(a)gmail.com> wrote: > On 2010-01-16, #! /shell/nerd wrote: > > > Hi, > > > I have a function MyFunc() and it prints some stuff & always returns > > 0. > > In order to suppress it I'm redirecting STDOUT to NULL. Now when I try > > > a. MyFunc >&- > > ExitStatus=$? > > I get the ExitStatus as 1. Where when I try > > > b. MyFunc >/dev/null > > ExitStatus=$? > > I get the ExitStatus as 0. > > Why ?? > > Did you not get an error messsage saying that you had a bad file > descriptor? > > '>&-' is incorrect. > > -- > Chris F.A. Johnson, author <http://shell.cfajohnson.com/> > =================================================================== > Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress) > Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress) > ===== My code in this post, if any, assumes the POSIX locale ===== > ===== and is released under the GNU General Public Licence ===== Yeah I did. But somewhere I read that we can do it.
From: Barry Margolin on 16 Jan 2010 00:20 In article <e5c4e76d-0413-4ab7-997d-523359d6a411(a)l19g2000yqb.googlegroups.com>, "#! /shell/nerd" <vikasera(a)gmail.com> wrote: > Hi, > > I have a function MyFunc() and it prints some stuff & always returns > 0. > In order to suppress it I'm redirecting STDOUT to NULL. Now when I try > > a. MyFunc >&- > ExitStatus=$? > I get the ExitStatus as 1. Where when I try > > b. MyFunc >/dev/null > ExitStatus=$? > I get the ExitStatus as 0. > Why ?? A function's exit status is the exit status of the last command in it. I presume that the last thing your function does is try to print something. Since you've closed stdout, this gets an error, and that error is propagated as the exit status of the function. -- Barry Margolin, barmar(a)alum.mit.edu Arlington, MA *** PLEASE post questions in newsgroups, not directly to me *** *** PLEASE don't copy me on replies, I'll read them in the group ***
From: Icarus Sparry on 16 Jan 2010 15:02 On Sat, 16 Jan 2010 04:40:39 +0000, Chris F.A. Johnson wrote: > On 2010-01-16, #! /shell/nerd wrote: >> Hi, >> >> I have a function MyFunc() and it prints some stuff & always returns 0. >> In order to suppress it I'm redirecting STDOUT to NULL. Now when I try >> >> a. MyFunc >&- >> ExitStatus=$? >> I get the ExitStatus as 1. Where when I try >> >> b. MyFunc >/dev/null >> ExitStatus=$? >> I get the ExitStatus as 0. >> Why ?? > > Did you not get an error messsage saying that you had a bad file > descriptor? > > '>&-' is incorrect. The redirection >&- is a perfectly good redirection, it is the short form of 1>&-, which says to close file descriptor 1 aka stdout. Barry has already explained why this probably causes the function to return an error indication.
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