---- BEGIN CONFIGURATION 1: Debian GNU/Linux 5.0 ----
Configuration Information [Automatically generated, do not change]:
Machine: i486
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='i486'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i486-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOC$
uname output: Linux griffo.sissa.it 2.6.26-2-686 #1 SMP Wed Aug 19
06:06:52 UTC 2009 i686 GNU/Linux
Machine Type: i486-pc-linux-gnu
Bash Version: 3.2
Patch Level: 39
Release Status: release
---- END CONFIGURATION 1 Debian GNU/Linux 5.0 ----
---- BEGIN CONFIGURATION 2: ./configure --prefix=<dir> under Debian
GNU/Linux 5.0 ----
Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='i686'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOC$
uname output: Linux griffo.sissa.it 2.6.26-2-686 #1 SMP Wed Aug 19
06:06:52 UTC 2009 i686 GNU/Linux
Machine Type: i686-pc-linux-gnu
Bash Version: 4.1
Patch Level: 9
Release Status: release
---- END CONFIGURATION 2: ./configure --prefix=<dir> under Debian
GNU/Linux 5.0 ----
Description:
CONFIGURATION 1: this is bash 3.2.39 you can find on Debian GNU/Linux
5.0
CONFIGURATION 2: this is bash 4.1.9 downloaded on a Debian GNU/Linux 5.0
machine and configured with
./configure --prefix=<dir>
I have tested the script below under both configurations above
and I found differences between "readonly" and "declare -r".
I was not able to find something justifying this behaviour in
the bash documentation.
The bug which manifests on the line 77.
Read the notes at the end.
---- begin script ----
1 function tst_readonly()
2 {
3 # - Declare a global variable since it is not
declared "local".
4 #
5 RO_VAR=f
6
7 # - The global variable defined above becomes readonly.
8 #
9 readonly RO_VAR
10 }
11
12 # - Call function tst_readonly to create global
variable and make it readonly
13 #
14 tst_readonly
15
16 # - Print the readonly variable contents;
17 # - The contents is ok.
18 #
19 echo "RO_VAR print 1: $RO_VAR"
20
21
22 # !!!!!!!!!!!!!!! Trying to assign a readonly variable
23 #
24 # - bash behaves correctly and prints an error message
and do not assigns
25 # any value to the readonly variable
26 #
27 RO_VAR=m
28
29
30 # - The readonly variable contents is still "f" since
the above assignment failed.
31 # - This is good.
32 #
33 echo "RO_VAR print 2: $RO_VAR"
34
35 echo
"-------------------------------------------------------------"
36
37 function tst_D_VAR_1()
38 {
39 # - Declare a global variable since it is not
declared "local".
40 #
41 D_VAR_1=d_var_1_first_assignment
42
43 # - The global variable defined above becomes readonly.
44 #
45 declare -r D_VAR_1
46
47
48 # !!!!!!!!!!!!!!! Trying to assign a readonly variable
49 #
50 # - bash behaves correctly and prints an error
message and do not assigns
51 # any value to the readonly variable
52 #
53 D_VAR_1=d_var_1_second_assignment
54
55
56 # - The readonly variable contents is still
"d_var_1_first_assignment" since the above assignment failed.
57 # - This is good.
58 #
59 # This following statement is not executed (isn't
this another bug?)
60 #
61 echo "D_VAR_1 print 1: $D_VAR_1"
62
63 }
64
65 # - Call function to create a readonly global variable
66 #
67 tst_D_VAR_1
68
69 # - print variable contents
70 # - The contents is ok; the second assignment in the
function did not work
71 #
72 echo "D_VAR_1 print 2: $D_VAR_1"
73
74 # - assign the global readonly variable
75 # - BUG : the assignment succeeds !!!!!!
76 #
77 D_VAR_1=d_var_1_third_assignment
78
79 echo "D_VAR_1 print 3: $D_VAR_1"
---- end script ----
a) "readonly" and "declare -r" do not behave the same way;
b) "declare -r" makes the variable readonly but only in a
function and this is not correct.
Repeat-By:
[Describe the sequence of events that causes the problem to occur.]
Fix:
1) In order to solve point b the bash behaviour should be
corrected since "declare -r" is not able to provide a
variable with the "readonly" attribute.
2) I find the behaviour of "readonly" correct since it is able
to give the readonly attribute to an existing variable. Nothing
to be done here.
regards
cristian zoicas
