Choosing program invocation name

[chipperMDW]

I seem to remember a utility or shell builtin that allows you to execute a command and "fake" the program invocation name (that is, what would go in a C program's [tt]argv[0][/tt]).

This facility exists because many programs behave differently based on how they are invoked. Most shells, for example, run as login shells when they are invoked with a name beginning with a dash. Programs like [tt]zip[/tt] and [tt]unzip[/tt] are typically the same executable, and decide how to behave by the name used to invoke them. (Though in that particular case, the "name-faking" is normally done by creating symlinks).

Anyway, I can't figure out the name of that utility. Can someone refresh my memory, please?

 

[hoinz]

do you mean $0 ?

 

[PHV]

A hardlink (ln) ?

Hope This Helps, PH.
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[chipperMDW]

No.

I would examine [tt]$0[/tt] to find the name used to invoke a script, whereas I'm looking for a utility that lets me invoke a program using a name that differs from the name of its executable file.


To clarify:

There's some utility that can be used in a manner similar to this:

invokeas foo bar arg1 arg2 arg3

That line would invoke the program [tt]bar[/tt], passing it the [tt]arg[/tt]s.

However, when [tt]bar[/tt] examines its arguments to discover the name used to invoke it, it will find [tt]foo[/tt], not [tt]bar[/tt].

[tt]invokeas[/tt] is a made-up name for this command, as I cannot remember its true name. I'm looking for that name.

 

[chipperMDW]

PHV,

Making a hard link would allow one to execute a program under a different name, but I was looking for the command to actually execute a program using an arbitrarily chosen name, as shown in my above example.


I found something close to what I was thinking of. [tt]exec -a[/tt] allows one to run a program and give it an arbitrary name.

However since [tt]exec[/tt] of course replaces the current shell with the [tt]exec[/tt]ed command, my above example is equivalent to:

sh -c "exec -a foo bar arg1 arg2 arg3"

What I'm remembering is a similar command that uses the syntax shown for the mythical [tt]invokeas[/tt] command in my example. That's what I'm looking for.

 

[jstreich]

Well, you could easily write a utility to this, as there is an exec that takes the command and argument string (which includes argv[0] )...

I know that there is command already, but I can't think of it off the top of my head...

 

[PHV]

This ?
(exec -a foo bar arg1 arg2 arg3)

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ222-2244

 

[chipperMDW]

Yeah, that'd work, and is pretty much equivalent to my second example.

Like I said, though, I'm not looking for some way to make it work. I know multiple ways of making it work. I could write a small shell script that has the functionality of my mythical [tt]invokeas[/tt] command by creating a temporary symlink, or by using [tt]exec -a[/tt]. I could similarly write a C program to do the same.

None of those help me, however, because my question isn't about accomplishing the task. My question is about a command name I cannot remember.

Again, what I'm looking for is the name of a certain already existing command that has the syntax of the mythical [tt]invokeas[/tt] used in my first example.

 

[jstreich]

Your not thinking of alias are you (I don't think you are, because it doesn't execute anything). I just thought of it b/c I thought it's man page might have a see also to the command you want, but it doesn't (at least on Debian linux).

 

[chipperMDW]

Nope.

I'm thinking it was named something like "runas" or "callas," but it doesn't appear to be either of those. I looked through the command names on my system that end in "as" and couldn't find anything.