Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > gnu.bash.bug > #15493

Re: Issues with history substitution and its documentation

Show key headers only | View raw

Hi,

This bug report has been my first one for Bash. I have not found how to
check the status of the bug. Would you please provide this information?

Below are a couple more issues I found.

There is an inconsistency with the documentation and behavior of the ^ word
designator. According to documentation, it refers to the first argument but
does not require a ':' before it if it starts the word designator. However,
it does not act like the numerical word designator 1 at the end of a range.

[root@localhost ~]# echo a b c
a b c
[root@localhost ~]# echo !!:1-1
echo a
a
[root@localhost ~]# echo a b c
a b c
[root@localhost ~]# echo !!:^-^
echo a b^
a b^

Also it is not explicitly documented that :- is equivalent to :0-

[root@localhost ~]# echo a b c d
a b c d
[root@localhost ~]# echo !!:-
echo echo a b c
echo a b c
[root@localhost ~]# echo a b c d
a b c d
[root@localhost ~]# echo !!:0-
echo echo a b c
echo a b c


Jim Monte

On Thu, Oct 3, 2019 at 6:19 PM Jim Monte <jim.monte01@gmail.com> wrote:

> Hi All,
>
> Below are some issues I found with history substitution. I am duplicating
> its behavior in a somewhat different use, and found issues with the
> documentation and bugs as described.
>
> Jim Monte
>
>
>
>
> From: jim
> To: bug-bash@gnu.org
> Subject: Issues with history substitution and its documentation
>
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
> -DCONF_OSTYPE='l$
> uname output: Linux T5500-Ubuntu 4.18.0-22-generic #23~18.04.1-Ubuntu SMP
> Thu J$
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 4.4
> Patch Level: 19
> Release Status: release
>
> Description:
>
> =============================================================================
> Documentation of quick substitution is incorrect (or does not match
> behavior).
>
> I believe this issue is an error with the documentation of history
> "Quick Substitution" that has existed since the first snapshot available at
> web.archive.org in 2007 at
>
>
> https://web.archive.org/web/20071223174140/http://www.gnu.org/software/bash/manual/html_node/Event-Designators.html
>
> At the least it is true that bash does not behave as the documentation
> states,
> but it does act in a way that is more reasonable (to me) than what is
> written.
>
> The documentation states that ^string1^string2^ is equivalent to
> !!:s/string1/string2/. However, bash treats it as equivalent to
> !!:s^string1^string2^.
>
> jim@T5500-Ubuntu:~$ echo /a
> /a
> jim@T5500-Ubuntu:~$ ^/a^b^
> echo b
> b
> jim@T5500-Ubuntu:~$ echo /a
> /a
> jim@T5500-Ubuntu:~$ !!:s//a/b/
> echo ab/
> ab/
> jim@T5500-Ubuntu:~$ echo /a
> /a
> jim@T5500-Ubuntu:~$ !!:s^/a^b^
> echo b
> b
>
>
> =============================================================================
> Behavior of empty "old" string in a substitution is undefined.
>
> The earlier example also shows a related but different issue with the
> !!:s//a/b/ command, where the string to locate is empty.
> It causes /a to be replaced by a and the b/ is appended.
>
> But
> jim@T5500-Ubuntu:~$ echo ///a
> ///a
> jim@T5500-Ubuntu:~$ !!:s//z/
> echo //z
> //z
>
> Here the empty string caused /a to be replaced by z.
>
> However,
> jim@T5500-Ubuntu:~$ echo ///abcdefg
> ///abcdefg
> jim@T5500-Ubuntu:~$ !!:s//z/
> echo //zbcdefg
> //zbcdefg
>
> Here a slash and the first character of the second word are replaced by z.
>
>
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:s//z/
> echo z b c
> z b c
>
>
> jim@T5500-Ubuntu:~$ echo ///
> ///
> jim@T5500-Ubuntu:~$ !!:s//z/
> bash: :s//z/: substitution failed
>
> Using :gs instead of :s does not change the results.
>
>
> =============================================================================
> BUG
> If an event designator has a leading - character, it is ignored.
>
> jim@T5500-Ubuntu:~/tmp$ cat main.c
> #include <stdio.h>
> int main(void)
> {
>     (void) fprintf(stdout, "Hello, world!\n");
>     return 0;
> }
>
> jim@T5500-Ubuntu:~/tmp$ gcc main.c -o"-a"
> jim@T5500-Ubuntu:~/tmp$ gcc main.c -o"-b"
> jim@T5500-Ubuntu:~/tmp$ -a
> Hello, world!
> jim@T5500-Ubuntu:~/tmp$ !-a:s/a/b
> bpt-cache abc
>
>
>
> =============================================================================
> Documentation of the :h and :t modifiers in section 9.3.3 is incomplete.
> :h removes the last / and everything after it if a / is present. Otherwise
> it does nothing.
>
> :t removes everything before and including the last / if one is present.
> Otherwise it does nothing.
>
> If a slash is present, !!:h/!!:t is equivalent to !!.
>
> jim@T5500-Ubuntu:~$ echo /a/b/c/d
> /a/b/c/d
> jim@T5500-Ubuntu:~$ !!:h
> echo /a/b/c
> /a/b/c
> jim@T5500-Ubuntu:~$ echo /a/b/c/d
> /a/b/c/d
> jim@T5500-Ubuntu:~$ !!:h:h
> echo /a/b
> /a/b
> jim@T5500-Ubuntu:~$ echo /a/b/c/d
> /a/b/c/d
> jim@T5500-Ubuntu:~$ !!:h:h:h
> echo /a
> /a
> jim@T5500-Ubuntu:~$ echo /a/b/c/d
> /a/b/c/d
> jim@T5500-Ubuntu:~$ !!:h:h:h:h
> echo
>
> jim@T5500-Ubuntu:~$
> jim@T5500-Ubuntu:~$ echo /a/b/c/d
> /a/b/c/d
> jim@T5500-Ubuntu:~$ !!:t
> d
> d: command not found
>
>
> jim@T5500-Ubuntu:~$ echo a/b
> a/b
> jim@T5500-Ubuntu:~$ !!:h/!!:t
> echo a/b
> a/b
> jim@T5500-Ubuntu:~$ echo a/b
> a/b
> jim@T5500-Ubuntu:~$ !!
> echo a/b
> a/b
>
>
>
> =============================================================================
> Documentation of the :r and :e modifiers is incomplete.
> :r removes the last ".suffix" and everything after it, if a ".suffix" is
> present. Otherwise it does nothing.
> :e leaves the last ".suffix" and everything after it, if a ".suffix" is
> present. Otherwise it does nothing.
>
> jim@T5500-Ubuntu:~$ echo .suffix a b .suffix c d
> .suffix a b .suffix c d
> jim@T5500-Ubuntu:~$ !!:r
> echo .suffix a b
> .suffix a b
> jim@T5500-Ubuntu:~$ echo .suffix a b .suffix c d
> .suffix a b .suffix c d
> jim@T5500-Ubuntu:~$ !!:r:r
> echo
>
> jim@T5500-Ubuntu:~$ echo .suffix a b  .suffix c d
> .suffix a b .suffix c d
> jim@T5500-Ubuntu:~$ !!:e
> .suffix c d
>
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:r
> echo a b c
> a b c
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:e
> echo a b c
> a b c
>
>
> =============================================================================
> BUG
> :p does not suppress execution if it is duplicated.
>
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:p
> echo a b c
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:p:p
> echo a b c
> a b c
>
>
> =============================================================================
> Documentation of :q and :x is incomplete.
> If :q and :x are repeated, the last specification is taken.
>
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:q
> 'echo a b c'
> echo a b c: command not found
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:x
> 'echo' 'a' 'b' 'c'
> a b c
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:q:x
> 'echo' 'a' 'b' 'c'
> a b c
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:q:x:q
> 'echo a b c'
> echo a b c: command not found
> jim@T5500-Ubuntu:~$ echo a b c
> a b c
> jim@T5500-Ubuntu:~$ !!:q:x:q:x
> 'echo' 'a' 'b' 'c'
> a b c
>
>
>  =============================================================================
> Finally, documentation of G should mention that it can be used with both
> :s and &.
>
>
>

Back to gnu.bash.bug | Previous | Next | Find similar | Unroll thread

Thread

Re: Issues with history substitution and its documentation Jim Monte <jim.monte01@gmail.com> - 2019-10-10 22:35 -0400

csiph-web