1. Forum
  2. Usenet
  3. COMP.UNIX.SHELL

  • Consequences of a hyphen as part of an identifier

    From Janis Papanagnou@21:1/5 to All on Sat Mar 19 01:01:42 2022
    From a post here I learned that bash (and zsh) allows a hyphen as
    part of a function identifier.

    Script:
    f-g() { echo 2; return 2; }
    f=7 g=3
    echo $(( f-g ))
    echo $( f-g )
    c-d=9

    Output:
    4
    2
    ...: c-d=9: command not found


    Do you consider that a sensible extension?

    Janis

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Ed Morton@21:1/5 to Janis Papanagnou on Fri Mar 18 20:23:17 2022
    On 3/18/2022 7:01 PM, Janis Papanagnou wrote:
    From a post here I learned that bash (and zsh) allows a hyphen as
    part of a function identifier.

    Script:
    f-g() { echo 2; return 2; }
    f=7 g=3
    echo $(( f-g ))
    echo $( f-g )
    c-d=9

    Output:
    4
    2
    ...: c-d=9: command not found


    Do you consider that a sensible extension?

    No, IMHO allowing more than C symbols (alphanumeric and underscore chars starting with an alpha or underscore) for function and script names is pointless, error-prone and annoying (trying to call foo_bar when the
    script is named foo-bar or vice-versa). This appears to be a case of
    "what can we do" over "what should we do".

    Ed.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Eli the Bearded@21:1/5 to mortonspam@gmail.com on Sat Mar 19 02:35:13 2022
    In comp.unix.shell, Ed Morton <mortonspam@gmail.com> wrote:
    On 3/18/2022 7:01 PM, Janis Papanagnou wrote:
    From a post here I learned that bash (and zsh) allows a hyphen as
    part of a function identifier.

    Aliases and functions seem to share nearly the same namespace that
    filenames have. I use ^? and ^H as alias names to set the backspace
    stty setting. The actual control characters, not the common display
    form.

    Ksh:

    alias ="stty erase '^?'"
    alias ="stty erase '^H'"

    (In bash, I can set both aliases, but the ^? generates a "command not
    found" error. ^H works. In ksh, both work.)

    Script:
    f-g() { echo 2; return 2; }
    f=7 g=3
    echo $(( f-g ))
    echo $( f-g )
    c-d=9

    Output:
    4
    2
    ...: c-d=9: command not found

    Variable names have a different set of rules, to be more "sensible".

    Do you consider that a sensible extension?

    Yes, since shell functions and aliases may be used to replace commands
    on the path, they should have the same rules for the identifiers.

    No, IMHO allowing more than C symbols (alphanumeric and underscore chars starting with an alpha or underscore) for function and script names is pointless, error-prone and annoying (trying to call foo_bar when the
    script is named foo-bar or vice-versa). This appears to be a case of
    "what can we do" over "what should we do".

    Or you haven't thought through the "replace a command on path" use.

    Bash:
    $ unalias [
    $ [[ $HOME ]] && echo ja
    ja
    $ [ $HOME ] && echo ja
    ja
    $ alias [=[[
    $ [ $HOME ] && echo ja
    bash: conditional binary operator expected
    bash: syntax error near `]'
    $ [ $HOME ]] && echo ja
    ja
    $

    Ksh gives me an error trying to use [ as an alias name. Bash lets me
    define and use a function [, ksh tells me the name is invalid.

    Bash:
    $ unalias [
    $ function [ { echo yo; }
    $ [
    yo
    $

    Elijah
    ------
    is unlikely to use exotic alias or function names except for very niche tasks

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Janis Papanagnou@21:1/5 to Ed Morton on Sat Mar 19 05:00:12 2022
    On 19.03.2022 02:23, Ed Morton wrote:
    On 3/18/2022 7:01 PM, Janis Papanagnou wrote:
    From a post here I learned that bash (and zsh) allows a hyphen as
    part of a function identifier.

    Script:
    f-g() { echo 2; return 2; }
    f=7 g=3
    echo $(( f-g ))
    echo $( f-g )
    c-d=9

    Output:
    4
    2
    ...: c-d=9: command not found


    Do you consider that a sensible extension?

    No, IMHO allowing more than C symbols (alphanumeric and underscore chars starting with an alpha or underscore) for function and script names is pointless, error-prone and annoying (trying to call foo_bar when the
    script is named foo-bar or vice-versa). This appears to be a case of
    "what can we do" over "what should we do".

    What I found disturbing with the above showed sample code is that the
    lexical parsing isn't deterministic any more; in one context "f-g" is
    tokenized as ID("f") OP("-") ID("g") and in the other context it's
    ID("f-g"). Apart from the language parsing aspect it's also harder
    for the coder (or code maintainer) to correctly interpret such code.

    Janis


    Ed.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Janis Papanagnou@21:1/5 to Eli the Bearded on Sat Mar 19 04:21:21 2022
    On 19.03.2022 03:35, Eli the Bearded wrote:
    In comp.unix.shell, Ed Morton <mortonspam@gmail.com> wrote:
    On 3/18/2022 7:01 PM, Janis Papanagnou wrote:
    Script:
    f-g() { echo 2; return 2; }
    f=7 g=3
    echo $(( f-g ))
    echo $( f-g )
    c-d=9

    Output:
    4
    2
    ...: c-d=9: command not found
    Do you consider that a sensible extension?

    Yes, since shell functions and aliases may be used to replace commands
    on the path, they should have the same rules for the identifiers.

    Interesting thought.

    But on the OS-level (defining commands) you can use almost every
    existing character to specify names of commands.

    Janis

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)