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List:       coreutils-bug
Subject:    bug#22045: expr substr returns with an error code 1 when the substring starts with 0
From:       Assaf Gordon <assafgordon () gmail ! com>
Date:       2015-11-28 23:38:00
Message-ID: 565A3AD8.7020108 () gmail ! com
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tag 22045 notabug
close 22045
stop

Hello,

On 11/28/2015 03:47 PM, Matthias Klose wrote:
> found with coreutils-8.23, expr substr returns with an error code when the \
> substring consists of only '0' characters, and the match is started at position 1.

> 
> $ expr substr 00001234 1 4; echo $?
> 0000
> 1
> $ expr substr 00001234 1 5; echo $?
> 00001
> 0

'expr' is unique in its exit-codes: exit codes of 0 or 1 *do not* indicate \
success/error, but whether the result evaluated to null or zero:

 From POSIX:
http://pubs.opengroup.org/onlinepubs/009695399/utilities/expr.html#tag_04_50_14
"
The following exit values shall be returned:
  0   The expression evaluates to neither null nor zero.
  1   The expression evaluates to null or zero.
  2   Invalid expression.
> 2   An error occurred.
"

And so, the exit codes you see indeed match the last computer value.

regards,
  - assaf


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