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Full Discussion: Unix Shell background processing
Top Forums Programming Unix Shell background processing Post 302457313 by Corona688 on Monday 27th of September 2010 06:08:21 PM
Old 09-27-2010
[edit] hang on

---------- Post updated at 04:04 PM ---------- Previous update was at 04:00 PM ----------

It could be crashing because you don't necessarily have 20 arguments. in which case you'll be feeding strcmp either garbage or NULL, either of which would cause it to crash. You'll need to remember how many arguments parseargs found(maybe put it through its return value instead of 'void'?)

In any case I don't think strcmp will do what you want. It returns 0 when the two strings are exactly the same, meaning, it'll only match on a line with no newlines containing nothing but &. I think you want strstr or strchr instead, see their man pages.

---------- Post updated at 04:08 PM ---------- Previous update was at 04:04 PM ----------

Code:
    switch(pid)
    {
        case -1:  
            cout << "DEBUG:Fork Failure" << endl;
            exit(-1);
            break;

        case  0:
            execvp(cmd[0], cmd);
            
            if(execvp(cmd[0], cmd) == -1)
            {
                cout << "Command Not Found" << endl;
                exit(0);
            }
            break;
   
        default:  
            wait(NULL);
            cout << "DEBUG:Child Finished" << endl;
            break;
    }

I'm surprised this even compiled, a break in the default section is mandatory in some common compilers.

Imagine case 0 without the break. If execvp() fails and doesn't catch the error it might keep going, and print "DEBUG: child finished" because the case statements don't tell it where to end, just where to begin. But with the break, it will leave that section of code entirely like you expected it to do.
 

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LEARN ABOUT REDHAT

split

SPLIT(1)								FSF								  SPLIT(1)

NAME

       split - split a file into pieces

SYNOPSIS

       split [OPTION] [INPUT [PREFIX]]

DESCRIPTION

       Output  fixed-size  pieces  of  INPUT  to PREFIXaa, PREFIXab, ...; default PREFIX is `x'.  With no INPUT, or when INPUT is -, read standard
       input.

       Mandatory arguments to long options are mandatory for short options too.

       -a, --suffix-length=N
	      use suffixes of length N (default 2)

       -b, --bytes=SIZE
	      put SIZE bytes per output file

       -C, --line-bytes=SIZE
	      put at most SIZE bytes of lines per output file

       -l, --lines=NUMBER
	      put NUMBER lines per output file

       --verbose
	      print a diagnostic to standard error just before each output file is opened

       --help display this help and exit

       --version
	      output version information and exit

       SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.

AUTHOR

       Written by Torbjorn Granlund and Richard M. Stallman.

REPORTING BUGS

       Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

       Copyright (C) 2002 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

SEE ALSO

       The  full  documentation  for split is maintained as a Texinfo manual.  If the info and split programs are properly installed at your site,
       the command

	      info split

       should give you access to the complete manual.

split (coreutils) 4.5.3 					   February 2003							  SPLIT(1)
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