NetBSD Problem Report #48201

From www@NetBSD.org  Tue Sep 10 04:56:58 2013
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Date: Tue, 10 Sep 2013 04:56:56 +0000 (UTC)
From: william@25thandclement.com
Reply-To: william@25thandclement.com
To: gnats-bugs@NetBSD.org
Subject: +noclobber option not POSIX compliant 
X-Send-Pr-Version: www-1.0

>Number:         48201
>Category:       bin
>Synopsis:       +noclobber option not POSIX compliant
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Sep 10 05:00:00 +0000 2013
>Closed-Date:    Mon May 30 06:04:34 +0000 2016
>Last-Modified:  Mon May 30 06:04:34 +0000 2016
>Originator:     William Ahern
>Release:        6.1.1
>Organization:
N/A
>Environment:
NetBSD  6.1.1 NetBSD 6.1.1 (GENERIC) amd64
>Description:
POSIX says: "Output redirection using the '>' format shall fail if the noclobber option is set (see the description of set -C) and the file named by the expansion of word exists and is a regular file."

However, with +noclobber NetBSD's sh fails when redirecting to /dev/null, a character device. I had to fix my scripts to use the append (>>) operator. FreeBSD, OpenBSD, Linux, Solaris, and OS X all behave as POSIX describes.



>How-To-Repeat:
sh -c 'set -C; printf "" >/dev/null'
>Fix:

>Release-Note:

>Audit-Trail:
From: Miwa Susumu <miwarin@gmail.com>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: bin/48201
Date: Wed, 15 Oct 2014 22:39:43 +0900

 import from FreeBSD
 https://svnweb.freebsd.org/base/head/bin/sh/redir.c

 --- /usr/src/bin/sh/redir.c.orig        2014-10-15 22:18:54.000000000 +0900
 +++ /usr/src/bin/sh/redir.c     2014-10-15 21:10:47.000000000 +0900
 @@ -173,10 +173,11 @@
  STATIC void
  openredirect(union node *redir, char memory[10], int flags)
  {
 +       struct stat sb;
         int fd = redir->nfile.fd;
         char *fname;
         int f;
 -       int oflags = O_WRONLY|O_CREAT|O_TRUNC, eflags;
 +       int eflags;

         /*
          * We suppress interrupts so that we won't leave open file
 @@ -203,12 +204,29 @@
                         goto ecreate;
                 break;
         case NTO:
 -               if (Cflag)
 -                       oflags |= O_EXCL;
 +               if (Cflag) {
 +                       fname = redir->nfile.expfname;
 +                       if (stat(fname, &sb) == -1) {
 +                               if ((f = open(fname,
 O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
 +                                       goto ecreate;
 +                       } else if (!S_ISREG(sb.st_mode)) {
 +                               if ((f = open(fname, O_WRONLY, 0666)) < 0)
 +                                       goto ecreate;
 +                               if (fstat(f, &sb) != -1 &&
 S_ISREG(sb.st_mode)) {
 +                                       close(f);
 +                                       errno = EEXIST;
 +                                       goto ecreate;
 +                               }
 +                       } else {
 +                               errno = EEXIST;
 +                               goto ecreate;
 +                       }
 +                       break;
 +               }
                 /* FALLTHROUGH */
         case NCLOBBER:
                 fname = redir->nfile.expfname;
 -               if ((f = open(fname, oflags, 0666)) < 0)
 +               if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
                         goto ecreate;
                 break;
         case NAPPEND:


 Detail
 ================================================

 Shell Command Language
  http://pubs.opengroup.org/onlinepubs/009604599/utilities/xcu_chap02.html

 <<<
 Output redirection using the '>' format shall fail if the noclobber
 option is set (see the description of set -C) and the file named by
 the expansion of word exists and is a regular file. Otherwise,
 redirection using the '>' or ">|" formats shall cause the file whose
 name results from the expansion of word to be created and opened for
 output on the designated file descriptor, or standard output if none
 is specified. If the file does not exist, it shall be created;
 otherwise, it shall be truncated to be an empty file after being
 opened
 >>>

 I think separately.
 --------
 (1) Output redirection using the '>' format shall fail
 if the noclobber option is set (see the description of set -C)
 the file named by the expansion of word exists
 is a regular file.

 (2) Otherwise, redirection using the '>' or ">|" formats shall cause
 the file whose name results from the expansion of word to be created
 opened for output on the designated file descriptor, or standard
 output if none is specified.

 (3) If the file does not exist,
 it shall be created;

 (4) otherwise,
 it shall be truncated to be an empty file after being opened
 --------


 The patch of the above, I verify the operation.
 --------
 (1) It is an error ... ok
 % touch hoge
 % /bin/sh -c 'set -C; printf "" > hoge'
 sh: cannot create hoge: file exists

 (2) can be written to /dev/null ... ok
 % /bin/sh -c 'set -C; printf "" > /dev/null'

 (3) hoge is generated ... ok
 % rm hoge
 % /bin/sh -c 'set -C; printf "" > hoge'
 % /bin/ls -l hoge
 -rw-r--r--  1 rin  users  0 Oct 15 22:36 hoge

 (4) hoge becomes empty ... ok
 % /bin/sh -c 'printf "hoge\n" > hoge'
 % cat hoge
 hoge
 %  /bin/sh -c 'printf "" > hoge'
 % cat hoge

 -- 
 miwarin

From: "Christos Zoulas" <christos@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/48201 CVS commit: src/bin/sh
Date: Wed, 15 Oct 2014 10:54:25 -0400

 Module Name:	src
 Committed By:	christos
 Date:		Wed Oct 15 14:54:25 UTC 2014

 Modified Files:
 	src/bin/sh: redir.c

 Log Message:
 PR/48201: Miwa Susumu: Fix set -C (no clobber) for POSIX; from FreeBSD
 Can't use O_EXCL because of device nodes; also truncate.


 To generate a diff of this commit:
 cvs rdiff -u -r1.35 -r1.36 src/bin/sh/redir.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: dholland@NetBSD.org
State-Changed-When: Mon, 30 May 2016 06:04:34 +0000
State-Changed-Why:
Committed by Christos in 2014


>Unformatted:

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