🚀 go-pugleaf

Joe Yang (yang@math.duke.edu) wrote:
: In article <3sprhr$6g6@venera.isi.edu>, Gaurav Singh <gsingh@isi.edu> wrote:
: >
: >Hi,
: >
: >	I am trying to execute the "system" command to execute an application
: >(executable program).
: >However the system command does not work if the name of the application has been
: >aliased.
: >
: >	e.g: $ alias test ps
: >	     $ test
: >		(this works)
: >	
: >	however system("test"); in a c-program does not work.
: >
: >	sh: test: not found
: >
: >	
: >	I wonder if there is a way to force the system command to take into
: >account the aliases, or is there a more efficient way to invoke an application
: >from a c-program.
: >

: The reason this doesn't work is because the "system" library routine
: spawns a Bourne shell process first, then execute the command in the
: new shell.  First of all, aliases are not part of the environment
: inherited by a child process ("sh" in this case), secondly, alias is
: a C shell command and Boune shell doesn't even understand it.

One quibble - a POSIX compatible system (and popen) execls
"/bin/posix/sh" which does support aliases.  However the syntax,

sh -cQ "command"

doesn't allow aliases.

Now,  does anyon know what the Q does?

: "system" is not a good way (although convinient) to apawn another
: program in a C program anyway, one of the disadventage is the overhead
: because another shell process is spawned unnecessarily.  Try using
: system call "fork" to create a new process directly and then using 
: exec (or one of its variations) to execute the new program.  Now this
: will not solve your alias program, because an alias is not a physical
: program.  Is there any particular reason you have to use an alias?
: this will make your grogram very "unportable" even from shell to
: shell.


: Rose Sun
: rose@ais.com

:  


: >	pl reply to this news group or to gsingh@isi.edu
: >
: >
: >	thanks a ton
: >
: >	Gaurav
: >
: >
: >
: >
: >
: >
: >
: >
: >



--
Dan Mercer                                            ClearSystems, Inc
Reply To:  damercer@mmm.com                           "The Mad Pedant"
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