Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!sri-spam!mordor!styx!ames!oliveb!intelca!intsc!inthap!polyof!john
From: john@polyof.UUCP ( John Buck )
Newsgroups: comp.lang.c
Subject: Re: Destroying arguments
Message-ID: <239@polyof.UUCP>
Date: Thu, 14-May-87 10:34:50 EDT
Article-I.D.: polyof.239
Posted: Thu May 14 10:34:50 1987
Date-Received: Sat, 16-May-87 11:22:37 EDT
References: <292@osupyr.UUCP>
Distribution: comp.unix.questions
Organization: Polytechnic Inst. of NY, Farmingdale NY
Lines: 26
Summary: changing command line args

In article <292@osupyr.UUCP>, dusan@osupyr.UUCP (Dusan Nedeljkovic) writes:
> I'm looking for a way to modify/destroy agruments passed to a C program
> on the command line.  I guess this would be similar to what crypt(1) does
> if a key is passed to it on the command line.  
> 

For each argv[] element you wish to destroy, simply copy another (any)
string (or string of characters) over it using strncpy() or a pointer
assignment loop:
   /* Note that the strlen() of any argument must not exceed the length
    * of the string of zeroes "00000000....0000"
    */
   for(i = 0; i < argc; i++)
      strncpy(argv[i], "0000000000000000000000000000000", strlen(argv[1]));

Note that you can't copy a string longer than the original argv[].
(You would scribble past the end!)

Also note, if you are trying to mask the name of the program you are running,
(namely, argv[0]), this method is not fool-proof.  Some version of "ps"
will print the u.u_comm field from the process' user structure.  This field
contains the basename of the program you are executing, and, there is no
way to change it short of an exec() type system call.

John Buck
polyof!john