Slightly confused about whether printf in the yash shell is a built-in command or not

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13















The yash shell has a printf built-in, according to its manual.



However, this is what I see in a yash shell with default configuration:



kk@eeyore ~ $ command -v printf
/usr/bin/printf
kk@eeyore ~ $ type printf
printf: a regular built-in at /usr/bin/printf


Is printf a built-in in this shell or not? The result is similar for a number of other supposedly built-in utilities that are also available as external commands.



As a comparison, in pdksh (ksh on OpenBSD, where printf is not a built-in):



$ command -v printf
/usr/bin/printf
$ type printf
printf is /usr/bin/printf


And in bash (where printf is a built-in):



$ command -v printf
printf
$ type printf
printf is a shell builtin









share|improve this question



















  • 1





    It's a built-in -- a regular, not a special built-in. If you're confused about the difference between special and regular built-ins, or behavior mandated by the standard (see command search and execution 1.e.i.a) -- which requires that a binary should exist in PATH in order for a regular built-in to be executed -- then please make your question about that.

    – mosvy
    Jan 23 at 17:30






  • 1





    @mosvy This was a detail of the standard that was unknown to me. If you want to turn that into an answer, I'd be happy. I don't think I would need to update the question for this to be an appropriate answer, as I was unaware of this particular detail. Or I'll write it myself later.

    – Kusalananda
    Jan 23 at 17:37
















13















The yash shell has a printf built-in, according to its manual.



However, this is what I see in a yash shell with default configuration:



kk@eeyore ~ $ command -v printf
/usr/bin/printf
kk@eeyore ~ $ type printf
printf: a regular built-in at /usr/bin/printf


Is printf a built-in in this shell or not? The result is similar for a number of other supposedly built-in utilities that are also available as external commands.



As a comparison, in pdksh (ksh on OpenBSD, where printf is not a built-in):



$ command -v printf
/usr/bin/printf
$ type printf
printf is /usr/bin/printf


And in bash (where printf is a built-in):



$ command -v printf
printf
$ type printf
printf is a shell builtin









share|improve this question



















  • 1





    It's a built-in -- a regular, not a special built-in. If you're confused about the difference between special and regular built-ins, or behavior mandated by the standard (see command search and execution 1.e.i.a) -- which requires that a binary should exist in PATH in order for a regular built-in to be executed -- then please make your question about that.

    – mosvy
    Jan 23 at 17:30






  • 1





    @mosvy This was a detail of the standard that was unknown to me. If you want to turn that into an answer, I'd be happy. I don't think I would need to update the question for this to be an appropriate answer, as I was unaware of this particular detail. Or I'll write it myself later.

    – Kusalananda
    Jan 23 at 17:37














13












13








13


1






The yash shell has a printf built-in, according to its manual.



However, this is what I see in a yash shell with default configuration:



kk@eeyore ~ $ command -v printf
/usr/bin/printf
kk@eeyore ~ $ type printf
printf: a regular built-in at /usr/bin/printf


Is printf a built-in in this shell or not? The result is similar for a number of other supposedly built-in utilities that are also available as external commands.



As a comparison, in pdksh (ksh on OpenBSD, where printf is not a built-in):



$ command -v printf
/usr/bin/printf
$ type printf
printf is /usr/bin/printf


And in bash (where printf is a built-in):



$ command -v printf
printf
$ type printf
printf is a shell builtin









share|improve this question
















The yash shell has a printf built-in, according to its manual.



However, this is what I see in a yash shell with default configuration:



kk@eeyore ~ $ command -v printf
/usr/bin/printf
kk@eeyore ~ $ type printf
printf: a regular built-in at /usr/bin/printf


Is printf a built-in in this shell or not? The result is similar for a number of other supposedly built-in utilities that are also available as external commands.



As a comparison, in pdksh (ksh on OpenBSD, where printf is not a built-in):



$ command -v printf
/usr/bin/printf
$ type printf
printf is /usr/bin/printf


And in bash (where printf is a built-in):



$ command -v printf
printf
$ type printf
printf is a shell builtin






posix printf shell-builtin yash






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Jan 23 at 18:51







Kusalananda

















asked Jan 23 at 16:38









KusalanandaKusalananda

129k16243400




129k16243400







  • 1





    It's a built-in -- a regular, not a special built-in. If you're confused about the difference between special and regular built-ins, or behavior mandated by the standard (see command search and execution 1.e.i.a) -- which requires that a binary should exist in PATH in order for a regular built-in to be executed -- then please make your question about that.

    – mosvy
    Jan 23 at 17:30






  • 1





    @mosvy This was a detail of the standard that was unknown to me. If you want to turn that into an answer, I'd be happy. I don't think I would need to update the question for this to be an appropriate answer, as I was unaware of this particular detail. Or I'll write it myself later.

    – Kusalananda
    Jan 23 at 17:37













  • 1





    It's a built-in -- a regular, not a special built-in. If you're confused about the difference between special and regular built-ins, or behavior mandated by the standard (see command search and execution 1.e.i.a) -- which requires that a binary should exist in PATH in order for a regular built-in to be executed -- then please make your question about that.

    – mosvy
    Jan 23 at 17:30






  • 1





    @mosvy This was a detail of the standard that was unknown to me. If you want to turn that into an answer, I'd be happy. I don't think I would need to update the question for this to be an appropriate answer, as I was unaware of this particular detail. Or I'll write it myself later.

    – Kusalananda
    Jan 23 at 17:37








1




1





It's a built-in -- a regular, not a special built-in. If you're confused about the difference between special and regular built-ins, or behavior mandated by the standard (see command search and execution 1.e.i.a) -- which requires that a binary should exist in PATH in order for a regular built-in to be executed -- then please make your question about that.

– mosvy
Jan 23 at 17:30





It's a built-in -- a regular, not a special built-in. If you're confused about the difference between special and regular built-ins, or behavior mandated by the standard (see command search and execution 1.e.i.a) -- which requires that a binary should exist in PATH in order for a regular built-in to be executed -- then please make your question about that.

– mosvy
Jan 23 at 17:30




1




1





@mosvy This was a detail of the standard that was unknown to me. If you want to turn that into an answer, I'd be happy. I don't think I would need to update the question for this to be an appropriate answer, as I was unaware of this particular detail. Or I'll write it myself later.

– Kusalananda
Jan 23 at 17:37






@mosvy This was a detail of the standard that was unknown to me. If you want to turn that into an answer, I'd be happy. I don't think I would need to update the question for this to be an appropriate answer, as I was unaware of this particular detail. Or I'll write it myself later.

– Kusalananda
Jan 23 at 17:37











3 Answers
3






active

oldest

votes


















13














The yash shell does have, and does use, a built-in version of printf (and other utilities). It just happens to be very pedantically POSIX compliant in the way it formulates the result of the command -v and type commands.



As mosvy comments, the POSIX standard requires that a regular built-in command be available as an external command in $PATH for the built-in version of the command to be executed.



This is the relevant text from the standard:




Command Search and Execution



If a simple command results in a command name and an optional list of arguments, the following actions shall be performed:




  1. If the command name does not contain any <slash> characters, the first successful step in the following sequence shall occur:




    • a. If the command name matches the name of a special built-in utility, that special built-in utility shall be invoked.



      [...]



    • e. Otherwise, the command shall be searched for using the PATH environment variable as described in XBD Environment Variables :

      • i. If the search is successful:

        • a. If the system has implemented the utility as a regular built-in or as a shell function, it shall be invoked at this point in the path search.

        • b. Otherwise, the shell executes the utility in a separate utility environment [...]

          [...]


      • ii. If the search is unsuccessful, the command shall fail with an exit status of 127 and the shell shall write an error message.



  2. If the command name contains at least one <slash>, [...]



This means that the output of command -v printf signifies that the printf command was found in the search path, while the output of type printf adds to this that the command is a regular built-in.



Since the printf command was found in the search path, and since it's a regular built-in in the shell, yash will call its built-in version of the command. If the printf was not found in the path, and if the yash shell was running in POSIX-ly correct mode, an error would have been generated instead.



yash prides itself on being a very POSIX compliant shell, and this is also true if we look at what POSIX says about command -v:




-v



Write a string to standard output that indicates the pathname or command that will be used by the shell, in the current shell execution environment (see Shell Execution Environment), to invoke command_name, but do not invoke command_name.



  • Utilities, regular built-in utilities, command_names including a <slash> character, and any implementation-defined functions that are found using the PATH variable (as described in Command Search and Execution), shall be written as absolute pathnames.






share|improve this answer




















  • 3





    Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

    – studog
    Jan 23 at 21:14











  • @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

    – Kusalananda
    Jan 23 at 21:49






  • 1





    Done: unix.stackexchange.com/questions/496341/…

    – studog
    Jan 23 at 22:28


















6














The Watanabe shell has three sorts of built-ins, described in detail in its manual. All of the built-in commands are also listed there, but one has to infer that something is a "regular" built-in command from the absence of any note saying that the command is a "special" or a "semi-special" built-in. Regular built-ins are unmarked.



printf is one such "regular" built-in. In native mode it is always invoked, irrespective of whether there is an external command found by that name.




$ PATH=/usr/bin
$ printf
printf: this command requires an operand
$ type printf
printf: a regular built-in at /usr/bin/printf
$
$ PATH=/
$ printf
printf: this command requires an operand
$ type printf
printf: a regular built-in (not found in $PATH)
$


But when the posixly-correct shell option is set it is only a built-in if the external command can be found on the PATH.




$ set --posixly-correct
$
$ PATH=/usr/bin
$ printf
printf: this command requires an operand
$
$ PATH=/
$ printf
yash: no such command `printf'
$


This is actually conformant to what the Single Unix Specifiation says, and has said since at least 1997.



It differs from the Z shell, the 93 Korn shell, the Bourne Again shell, and the Debian Almquist shell, none of which either implement or document such behaviour for regular built-ins. The Z shell, for example, documents that regular built-ins are always found, before the step that searches PATH. So too does the Debian Almquist shell. And that's what these shells all do, even if invoked as sh with their turn-on-POSIX options.




% /bin/exec -a sh zsh -c "PATH=/ ; type printf ; printf"
printf is a shell builtin
zsh:printf:1: not enough arguments
% /bin/exec -a sh ksh93 -c "PATH=/ ; type printf ; printf"
printf is a shell builtin
Usage: printf [ options ] format [string ...]
% /bin/exec -a sh bash --posix -c "PATH=/ type printf ; printf"
printf is a shell builtin
printf: usage: printf [-v var] format [arguments]
% /bin/exec -a sh dash -c "PATH=/ ; type printf ; printf"
printf is a shell builtin
sh: 1: printf: usage: printf format [arg ...]
%


However, not running printf when it is not on the PATH is the behaviour of the PD Korn shell, the Heirloom Bourne shell, and the MirBSD Korn shell; because they do not have a printf built-in in the first place. ☺




% /bin/exec -a sh `command -v ksh` -c "PATH=/ ; type printf ; printf"
printf not found
sh: printf: not found
% /bin/exec -a sh `command -v oksh` -c "PATH=/ ; type printf ; printf"
printf not found
sh: printf: not found
% /bin/exec -a sh `command -v jsh` -c "PATH=/ ; type printf ; printf"
printf not found
sh: printf: not found
% /bin/exec -a sh mksh -c "PATH=/ ; type printf ; printf"
printf not found
sh: printf: not found
% ksh -c "type printf ; printf"
printf is a tracked alias for /usr/bin/printf
usage: printf format [arguments ...]
% oksh -c "type printf ; printf"
printf is a tracked alias for /usr/bin/printf
usage: printf format [arguments ...]
% jsh -c "type printf ; printf"
printf is hashed (/usr/bin/printf)
usage: printf format [arguments ...]
% mksh -c "type printf ; printf"
printf is a tracked alias for /usr/bin/printf
usage: printf format [arguments ...]
$





share|improve this answer























  • Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

    – Kusalananda
    Jan 23 at 19:03



















-1














The wording could be improved.



If the shell is in posix mode: set --posixly-correct:



For regular built-ins that do not exist in the PATH this is printed:



pushd: a regular built-in (not found in $PATH)


Which is a clear description: It is a builtin but there is no executable with the same name in the PATH.



However, for regular built-ins which name also exist in the PATH, this is printed:



echo: a regular built-in at /bin/echo


Which, seems to imply that the executable at /bin/echo will be executed (which will not be). I suggest that a change from at to also found in PATH at:



echo: a regular built-in also found in PATH at /bin/echo


would make a better description. Maybe enclosing that in parenthesis (as the other answer did) could make it better.




In POSIX mode, no regular builtin will work unless it is also found in the PATH.



However, both (POSIX) special:



break colon continue dot eval exec exit export
readonly return set shift times trap unset


And yash's semi-special (not special for POSIX):



alias bg cd command false fc fg getopts jobs
kill pwd read true umask unalias wait


builtins still work.






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    3 Answers
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    3 Answers
    3






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    active

    oldest

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    13














    The yash shell does have, and does use, a built-in version of printf (and other utilities). It just happens to be very pedantically POSIX compliant in the way it formulates the result of the command -v and type commands.



    As mosvy comments, the POSIX standard requires that a regular built-in command be available as an external command in $PATH for the built-in version of the command to be executed.



    This is the relevant text from the standard:




    Command Search and Execution



    If a simple command results in a command name and an optional list of arguments, the following actions shall be performed:




    1. If the command name does not contain any <slash> characters, the first successful step in the following sequence shall occur:




      • a. If the command name matches the name of a special built-in utility, that special built-in utility shall be invoked.



        [...]



      • e. Otherwise, the command shall be searched for using the PATH environment variable as described in XBD Environment Variables :

        • i. If the search is successful:

          • a. If the system has implemented the utility as a regular built-in or as a shell function, it shall be invoked at this point in the path search.

          • b. Otherwise, the shell executes the utility in a separate utility environment [...]

            [...]


        • ii. If the search is unsuccessful, the command shall fail with an exit status of 127 and the shell shall write an error message.



    2. If the command name contains at least one <slash>, [...]



    This means that the output of command -v printf signifies that the printf command was found in the search path, while the output of type printf adds to this that the command is a regular built-in.



    Since the printf command was found in the search path, and since it's a regular built-in in the shell, yash will call its built-in version of the command. If the printf was not found in the path, and if the yash shell was running in POSIX-ly correct mode, an error would have been generated instead.



    yash prides itself on being a very POSIX compliant shell, and this is also true if we look at what POSIX says about command -v:




    -v



    Write a string to standard output that indicates the pathname or command that will be used by the shell, in the current shell execution environment (see Shell Execution Environment), to invoke command_name, but do not invoke command_name.



    • Utilities, regular built-in utilities, command_names including a <slash> character, and any implementation-defined functions that are found using the PATH variable (as described in Command Search and Execution), shall be written as absolute pathnames.






    share|improve this answer




















    • 3





      Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

      – studog
      Jan 23 at 21:14











    • @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

      – Kusalananda
      Jan 23 at 21:49






    • 1





      Done: unix.stackexchange.com/questions/496341/…

      – studog
      Jan 23 at 22:28















    13














    The yash shell does have, and does use, a built-in version of printf (and other utilities). It just happens to be very pedantically POSIX compliant in the way it formulates the result of the command -v and type commands.



    As mosvy comments, the POSIX standard requires that a regular built-in command be available as an external command in $PATH for the built-in version of the command to be executed.



    This is the relevant text from the standard:




    Command Search and Execution



    If a simple command results in a command name and an optional list of arguments, the following actions shall be performed:




    1. If the command name does not contain any <slash> characters, the first successful step in the following sequence shall occur:




      • a. If the command name matches the name of a special built-in utility, that special built-in utility shall be invoked.



        [...]



      • e. Otherwise, the command shall be searched for using the PATH environment variable as described in XBD Environment Variables :

        • i. If the search is successful:

          • a. If the system has implemented the utility as a regular built-in or as a shell function, it shall be invoked at this point in the path search.

          • b. Otherwise, the shell executes the utility in a separate utility environment [...]

            [...]


        • ii. If the search is unsuccessful, the command shall fail with an exit status of 127 and the shell shall write an error message.



    2. If the command name contains at least one <slash>, [...]



    This means that the output of command -v printf signifies that the printf command was found in the search path, while the output of type printf adds to this that the command is a regular built-in.



    Since the printf command was found in the search path, and since it's a regular built-in in the shell, yash will call its built-in version of the command. If the printf was not found in the path, and if the yash shell was running in POSIX-ly correct mode, an error would have been generated instead.



    yash prides itself on being a very POSIX compliant shell, and this is also true if we look at what POSIX says about command -v:




    -v



    Write a string to standard output that indicates the pathname or command that will be used by the shell, in the current shell execution environment (see Shell Execution Environment), to invoke command_name, but do not invoke command_name.



    • Utilities, regular built-in utilities, command_names including a <slash> character, and any implementation-defined functions that are found using the PATH variable (as described in Command Search and Execution), shall be written as absolute pathnames.






    share|improve this answer




















    • 3





      Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

      – studog
      Jan 23 at 21:14











    • @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

      – Kusalananda
      Jan 23 at 21:49






    • 1





      Done: unix.stackexchange.com/questions/496341/…

      – studog
      Jan 23 at 22:28













    13












    13








    13







    The yash shell does have, and does use, a built-in version of printf (and other utilities). It just happens to be very pedantically POSIX compliant in the way it formulates the result of the command -v and type commands.



    As mosvy comments, the POSIX standard requires that a regular built-in command be available as an external command in $PATH for the built-in version of the command to be executed.



    This is the relevant text from the standard:




    Command Search and Execution



    If a simple command results in a command name and an optional list of arguments, the following actions shall be performed:




    1. If the command name does not contain any <slash> characters, the first successful step in the following sequence shall occur:




      • a. If the command name matches the name of a special built-in utility, that special built-in utility shall be invoked.



        [...]



      • e. Otherwise, the command shall be searched for using the PATH environment variable as described in XBD Environment Variables :

        • i. If the search is successful:

          • a. If the system has implemented the utility as a regular built-in or as a shell function, it shall be invoked at this point in the path search.

          • b. Otherwise, the shell executes the utility in a separate utility environment [...]

            [...]


        • ii. If the search is unsuccessful, the command shall fail with an exit status of 127 and the shell shall write an error message.



    2. If the command name contains at least one <slash>, [...]



    This means that the output of command -v printf signifies that the printf command was found in the search path, while the output of type printf adds to this that the command is a regular built-in.



    Since the printf command was found in the search path, and since it's a regular built-in in the shell, yash will call its built-in version of the command. If the printf was not found in the path, and if the yash shell was running in POSIX-ly correct mode, an error would have been generated instead.



    yash prides itself on being a very POSIX compliant shell, and this is also true if we look at what POSIX says about command -v:




    -v



    Write a string to standard output that indicates the pathname or command that will be used by the shell, in the current shell execution environment (see Shell Execution Environment), to invoke command_name, but do not invoke command_name.



    • Utilities, regular built-in utilities, command_names including a <slash> character, and any implementation-defined functions that are found using the PATH variable (as described in Command Search and Execution), shall be written as absolute pathnames.






    share|improve this answer















    The yash shell does have, and does use, a built-in version of printf (and other utilities). It just happens to be very pedantically POSIX compliant in the way it formulates the result of the command -v and type commands.



    As mosvy comments, the POSIX standard requires that a regular built-in command be available as an external command in $PATH for the built-in version of the command to be executed.



    This is the relevant text from the standard:




    Command Search and Execution



    If a simple command results in a command name and an optional list of arguments, the following actions shall be performed:




    1. If the command name does not contain any <slash> characters, the first successful step in the following sequence shall occur:




      • a. If the command name matches the name of a special built-in utility, that special built-in utility shall be invoked.



        [...]



      • e. Otherwise, the command shall be searched for using the PATH environment variable as described in XBD Environment Variables :

        • i. If the search is successful:

          • a. If the system has implemented the utility as a regular built-in or as a shell function, it shall be invoked at this point in the path search.

          • b. Otherwise, the shell executes the utility in a separate utility environment [...]

            [...]


        • ii. If the search is unsuccessful, the command shall fail with an exit status of 127 and the shell shall write an error message.



    2. If the command name contains at least one <slash>, [...]



    This means that the output of command -v printf signifies that the printf command was found in the search path, while the output of type printf adds to this that the command is a regular built-in.



    Since the printf command was found in the search path, and since it's a regular built-in in the shell, yash will call its built-in version of the command. If the printf was not found in the path, and if the yash shell was running in POSIX-ly correct mode, an error would have been generated instead.



    yash prides itself on being a very POSIX compliant shell, and this is also true if we look at what POSIX says about command -v:




    -v



    Write a string to standard output that indicates the pathname or command that will be used by the shell, in the current shell execution environment (see Shell Execution Environment), to invoke command_name, but do not invoke command_name.



    • Utilities, regular built-in utilities, command_names including a <slash> character, and any implementation-defined functions that are found using the PATH variable (as described in Command Search and Execution), shall be written as absolute pathnames.







    share|improve this answer














    share|improve this answer



    share|improve this answer








    edited Jan 24 at 7:29

























    answered Jan 23 at 18:46









    KusalanandaKusalananda

    129k16243400




    129k16243400







    • 3





      Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

      – studog
      Jan 23 at 21:14











    • @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

      – Kusalananda
      Jan 23 at 21:49






    • 1





      Done: unix.stackexchange.com/questions/496341/…

      – studog
      Jan 23 at 22:28












    • 3





      Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

      – studog
      Jan 23 at 21:14











    • @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

      – Kusalananda
      Jan 23 at 21:49






    • 1





      Done: unix.stackexchange.com/questions/496341/…

      – studog
      Jan 23 at 22:28







    3




    3





    Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

    – studog
    Jan 23 at 21:14





    Does anyone know why POSIX has this requirement for an external command to exist before running the built-in command?

    – studog
    Jan 23 at 21:14













    @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

    – Kusalananda
    Jan 23 at 21:49





    @studog You may want to ask that as a separate new question, possibly referring to this answer and/or question.

    – Kusalananda
    Jan 23 at 21:49




    1




    1





    Done: unix.stackexchange.com/questions/496341/…

    – studog
    Jan 23 at 22:28





    Done: unix.stackexchange.com/questions/496341/…

    – studog
    Jan 23 at 22:28













    6














    The Watanabe shell has three sorts of built-ins, described in detail in its manual. All of the built-in commands are also listed there, but one has to infer that something is a "regular" built-in command from the absence of any note saying that the command is a "special" or a "semi-special" built-in. Regular built-ins are unmarked.



    printf is one such "regular" built-in. In native mode it is always invoked, irrespective of whether there is an external command found by that name.




    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in at /usr/bin/printf
    $
    $ PATH=/
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in (not found in $PATH)
    $


    But when the posixly-correct shell option is set it is only a built-in if the external command can be found on the PATH.




    $ set --posixly-correct
    $
    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $
    $ PATH=/
    $ printf
    yash: no such command `printf'
    $


    This is actually conformant to what the Single Unix Specifiation says, and has said since at least 1997.



    It differs from the Z shell, the 93 Korn shell, the Bourne Again shell, and the Debian Almquist shell, none of which either implement or document such behaviour for regular built-ins. The Z shell, for example, documents that regular built-ins are always found, before the step that searches PATH. So too does the Debian Almquist shell. And that's what these shells all do, even if invoked as sh with their turn-on-POSIX options.




    % /bin/exec -a sh zsh -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    zsh:printf:1: not enough arguments
    % /bin/exec -a sh ksh93 -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    Usage: printf [ options ] format [string ...]
    % /bin/exec -a sh bash --posix -c "PATH=/ type printf ; printf"
    printf is a shell builtin
    printf: usage: printf [-v var] format [arguments]
    % /bin/exec -a sh dash -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    sh: 1: printf: usage: printf format [arg ...]
    %


    However, not running printf when it is not on the PATH is the behaviour of the PD Korn shell, the Heirloom Bourne shell, and the MirBSD Korn shell; because they do not have a printf built-in in the first place. ☺




    % /bin/exec -a sh `command -v ksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v oksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v jsh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh mksh -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % ksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % oksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % jsh -c "type printf ; printf"
    printf is hashed (/usr/bin/printf)
    usage: printf format [arguments ...]
    % mksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    $





    share|improve this answer























    • Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

      – Kusalananda
      Jan 23 at 19:03
















    6














    The Watanabe shell has three sorts of built-ins, described in detail in its manual. All of the built-in commands are also listed there, but one has to infer that something is a "regular" built-in command from the absence of any note saying that the command is a "special" or a "semi-special" built-in. Regular built-ins are unmarked.



    printf is one such "regular" built-in. In native mode it is always invoked, irrespective of whether there is an external command found by that name.




    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in at /usr/bin/printf
    $
    $ PATH=/
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in (not found in $PATH)
    $


    But when the posixly-correct shell option is set it is only a built-in if the external command can be found on the PATH.




    $ set --posixly-correct
    $
    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $
    $ PATH=/
    $ printf
    yash: no such command `printf'
    $


    This is actually conformant to what the Single Unix Specifiation says, and has said since at least 1997.



    It differs from the Z shell, the 93 Korn shell, the Bourne Again shell, and the Debian Almquist shell, none of which either implement or document such behaviour for regular built-ins. The Z shell, for example, documents that regular built-ins are always found, before the step that searches PATH. So too does the Debian Almquist shell. And that's what these shells all do, even if invoked as sh with their turn-on-POSIX options.




    % /bin/exec -a sh zsh -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    zsh:printf:1: not enough arguments
    % /bin/exec -a sh ksh93 -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    Usage: printf [ options ] format [string ...]
    % /bin/exec -a sh bash --posix -c "PATH=/ type printf ; printf"
    printf is a shell builtin
    printf: usage: printf [-v var] format [arguments]
    % /bin/exec -a sh dash -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    sh: 1: printf: usage: printf format [arg ...]
    %


    However, not running printf when it is not on the PATH is the behaviour of the PD Korn shell, the Heirloom Bourne shell, and the MirBSD Korn shell; because they do not have a printf built-in in the first place. ☺




    % /bin/exec -a sh `command -v ksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v oksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v jsh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh mksh -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % ksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % oksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % jsh -c "type printf ; printf"
    printf is hashed (/usr/bin/printf)
    usage: printf format [arguments ...]
    % mksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    $





    share|improve this answer























    • Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

      – Kusalananda
      Jan 23 at 19:03














    6












    6








    6







    The Watanabe shell has three sorts of built-ins, described in detail in its manual. All of the built-in commands are also listed there, but one has to infer that something is a "regular" built-in command from the absence of any note saying that the command is a "special" or a "semi-special" built-in. Regular built-ins are unmarked.



    printf is one such "regular" built-in. In native mode it is always invoked, irrespective of whether there is an external command found by that name.




    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in at /usr/bin/printf
    $
    $ PATH=/
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in (not found in $PATH)
    $


    But when the posixly-correct shell option is set it is only a built-in if the external command can be found on the PATH.




    $ set --posixly-correct
    $
    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $
    $ PATH=/
    $ printf
    yash: no such command `printf'
    $


    This is actually conformant to what the Single Unix Specifiation says, and has said since at least 1997.



    It differs from the Z shell, the 93 Korn shell, the Bourne Again shell, and the Debian Almquist shell, none of which either implement or document such behaviour for regular built-ins. The Z shell, for example, documents that regular built-ins are always found, before the step that searches PATH. So too does the Debian Almquist shell. And that's what these shells all do, even if invoked as sh with their turn-on-POSIX options.




    % /bin/exec -a sh zsh -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    zsh:printf:1: not enough arguments
    % /bin/exec -a sh ksh93 -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    Usage: printf [ options ] format [string ...]
    % /bin/exec -a sh bash --posix -c "PATH=/ type printf ; printf"
    printf is a shell builtin
    printf: usage: printf [-v var] format [arguments]
    % /bin/exec -a sh dash -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    sh: 1: printf: usage: printf format [arg ...]
    %


    However, not running printf when it is not on the PATH is the behaviour of the PD Korn shell, the Heirloom Bourne shell, and the MirBSD Korn shell; because they do not have a printf built-in in the first place. ☺




    % /bin/exec -a sh `command -v ksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v oksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v jsh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh mksh -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % ksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % oksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % jsh -c "type printf ; printf"
    printf is hashed (/usr/bin/printf)
    usage: printf format [arguments ...]
    % mksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    $





    share|improve this answer













    The Watanabe shell has three sorts of built-ins, described in detail in its manual. All of the built-in commands are also listed there, but one has to infer that something is a "regular" built-in command from the absence of any note saying that the command is a "special" or a "semi-special" built-in. Regular built-ins are unmarked.



    printf is one such "regular" built-in. In native mode it is always invoked, irrespective of whether there is an external command found by that name.




    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in at /usr/bin/printf
    $
    $ PATH=/
    $ printf
    printf: this command requires an operand
    $ type printf
    printf: a regular built-in (not found in $PATH)
    $


    But when the posixly-correct shell option is set it is only a built-in if the external command can be found on the PATH.




    $ set --posixly-correct
    $
    $ PATH=/usr/bin
    $ printf
    printf: this command requires an operand
    $
    $ PATH=/
    $ printf
    yash: no such command `printf'
    $


    This is actually conformant to what the Single Unix Specifiation says, and has said since at least 1997.



    It differs from the Z shell, the 93 Korn shell, the Bourne Again shell, and the Debian Almquist shell, none of which either implement or document such behaviour for regular built-ins. The Z shell, for example, documents that regular built-ins are always found, before the step that searches PATH. So too does the Debian Almquist shell. And that's what these shells all do, even if invoked as sh with their turn-on-POSIX options.




    % /bin/exec -a sh zsh -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    zsh:printf:1: not enough arguments
    % /bin/exec -a sh ksh93 -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    Usage: printf [ options ] format [string ...]
    % /bin/exec -a sh bash --posix -c "PATH=/ type printf ; printf"
    printf is a shell builtin
    printf: usage: printf [-v var] format [arguments]
    % /bin/exec -a sh dash -c "PATH=/ ; type printf ; printf"
    printf is a shell builtin
    sh: 1: printf: usage: printf format [arg ...]
    %


    However, not running printf when it is not on the PATH is the behaviour of the PD Korn shell, the Heirloom Bourne shell, and the MirBSD Korn shell; because they do not have a printf built-in in the first place. ☺




    % /bin/exec -a sh `command -v ksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v oksh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh `command -v jsh` -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % /bin/exec -a sh mksh -c "PATH=/ ; type printf ; printf"
    printf not found
    sh: printf: not found
    % ksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % oksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    % jsh -c "type printf ; printf"
    printf is hashed (/usr/bin/printf)
    usage: printf format [arguments ...]
    % mksh -c "type printf ; printf"
    printf is a tracked alias for /usr/bin/printf
    usage: printf format [arguments ...]
    $






    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered Jan 23 at 18:55









    JdeBPJdeBP

    34.8k470163




    34.8k470163












    • Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

      – Kusalananda
      Jan 23 at 19:03


















    • Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

      – Kusalananda
      Jan 23 at 19:03

















    Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

    – Kusalananda
    Jan 23 at 19:03






    Good! Thanks for confirming and for adding the shell-specific bits to my knowledge! I like this shell more already.

    – Kusalananda
    Jan 23 at 19:03












    -1














    The wording could be improved.



    If the shell is in posix mode: set --posixly-correct:



    For regular built-ins that do not exist in the PATH this is printed:



    pushd: a regular built-in (not found in $PATH)


    Which is a clear description: It is a builtin but there is no executable with the same name in the PATH.



    However, for regular built-ins which name also exist in the PATH, this is printed:



    echo: a regular built-in at /bin/echo


    Which, seems to imply that the executable at /bin/echo will be executed (which will not be). I suggest that a change from at to also found in PATH at:



    echo: a regular built-in also found in PATH at /bin/echo


    would make a better description. Maybe enclosing that in parenthesis (as the other answer did) could make it better.




    In POSIX mode, no regular builtin will work unless it is also found in the PATH.



    However, both (POSIX) special:



    break colon continue dot eval exec exit export
    readonly return set shift times trap unset


    And yash's semi-special (not special for POSIX):



    alias bg cd command false fc fg getopts jobs
    kill pwd read true umask unalias wait


    builtins still work.






    share|improve this answer





























      -1














      The wording could be improved.



      If the shell is in posix mode: set --posixly-correct:



      For regular built-ins that do not exist in the PATH this is printed:



      pushd: a regular built-in (not found in $PATH)


      Which is a clear description: It is a builtin but there is no executable with the same name in the PATH.



      However, for regular built-ins which name also exist in the PATH, this is printed:



      echo: a regular built-in at /bin/echo


      Which, seems to imply that the executable at /bin/echo will be executed (which will not be). I suggest that a change from at to also found in PATH at:



      echo: a regular built-in also found in PATH at /bin/echo


      would make a better description. Maybe enclosing that in parenthesis (as the other answer did) could make it better.




      In POSIX mode, no regular builtin will work unless it is also found in the PATH.



      However, both (POSIX) special:



      break colon continue dot eval exec exit export
      readonly return set shift times trap unset


      And yash's semi-special (not special for POSIX):



      alias bg cd command false fc fg getopts jobs
      kill pwd read true umask unalias wait


      builtins still work.






      share|improve this answer



























        -1












        -1








        -1







        The wording could be improved.



        If the shell is in posix mode: set --posixly-correct:



        For regular built-ins that do not exist in the PATH this is printed:



        pushd: a regular built-in (not found in $PATH)


        Which is a clear description: It is a builtin but there is no executable with the same name in the PATH.



        However, for regular built-ins which name also exist in the PATH, this is printed:



        echo: a regular built-in at /bin/echo


        Which, seems to imply that the executable at /bin/echo will be executed (which will not be). I suggest that a change from at to also found in PATH at:



        echo: a regular built-in also found in PATH at /bin/echo


        would make a better description. Maybe enclosing that in parenthesis (as the other answer did) could make it better.




        In POSIX mode, no regular builtin will work unless it is also found in the PATH.



        However, both (POSIX) special:



        break colon continue dot eval exec exit export
        readonly return set shift times trap unset


        And yash's semi-special (not special for POSIX):



        alias bg cd command false fc fg getopts jobs
        kill pwd read true umask unalias wait


        builtins still work.






        share|improve this answer















        The wording could be improved.



        If the shell is in posix mode: set --posixly-correct:



        For regular built-ins that do not exist in the PATH this is printed:



        pushd: a regular built-in (not found in $PATH)


        Which is a clear description: It is a builtin but there is no executable with the same name in the PATH.



        However, for regular built-ins which name also exist in the PATH, this is printed:



        echo: a regular built-in at /bin/echo


        Which, seems to imply that the executable at /bin/echo will be executed (which will not be). I suggest that a change from at to also found in PATH at:



        echo: a regular built-in also found in PATH at /bin/echo


        would make a better description. Maybe enclosing that in parenthesis (as the other answer did) could make it better.




        In POSIX mode, no regular builtin will work unless it is also found in the PATH.



        However, both (POSIX) special:



        break colon continue dot eval exec exit export
        readonly return set shift times trap unset


        And yash's semi-special (not special for POSIX):



        alias bg cd command false fc fg getopts jobs
        kill pwd read true umask unalias wait


        builtins still work.







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Jan 25 at 2:05

























        answered Jan 23 at 19:26









        IsaacIsaac

        11.8k11752




        11.8k11752



























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