out-of-range-offset or zero-length substring parameter expansion

[Lorenzo Viali]

Configuration Information [Automatically generated, do
not change]:
Machine: i386
OS: linux-gnu
Compiler: i386-pc-linux-gnu-gcc
Compilation CFLAGS:  -DPROGRAM='bash'
-DCONF_HOSTTYPE='i386' -DCONF_OSTYPE='linux-gnu'
-DCONF_MACHTYPE='i386-pc-linux-gnu' -DCONF_VENDOR='pc'
-DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib
  -Os -mcpu=i686 -pipe
uname output: Linux gseba-mobile 2.6.18-rc7 #3 Fri Sep
22 18:37:46 GMT 2006 i686 Mobile AMD Sempron(tm)
Processor 3300+ AuthenticAMD GNU/Linux
Machine Type: i386-pc-linux-gnu

Bash Version: 3.1
Patch Level: 17
Release Status: release

Description:
        when taking the substring of a variable, in
certain conditions, it behaves differently whether or
not is surrounded by other strings

Repeat-By:
        $ x="alfa"
        $ echo ${#x}
        4
        $ # now we're taking the substring of x
        $ # starting from index 4 (should be null)
        $ [ "${x:4}" == "" ] && echo ok
        ok
        $ # now we're taking the substring of x
        $ # starting from index 4, but we wrap
        $ # it between `|' (should be `||')
        $ [ "|${x:4}|" == "||" ] && echo ok
        $ # nothing was echoed
        $ # 
        $ # now we're taking a substring of x
        $ # of length 0 (should be null)
        $ [ "${x::0}" == "" ] && echo ok
        ok
        $ # now we're taking a substring of x
        $ # of length 0, but we wrap
        $ # it between `|' (should be `||')
        $ [ "|${x::0}|" == "||" ] && echo ok
        $ # nothing was echoed


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