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Full Discussion: Retrieving command line arguments of a particular PID
Top Forums UNIX for Advanced & Expert Users Retrieving command line arguments of a particular PID Post 302252171 by Andrewkl on Tuesday 28th of October 2008 10:05:38 PM
Old 10-28-2008
hi,

Thank you for the tip.

I am able to read in the contents of the "cmdline" file into a variable,
but when I try to print out the string, the output shows only characters before
the first null character.

How do I get the other characters after the first null character.
You suggested that i use pointer arithmetic, but how do i'm not sure
how to get the index of the '\0'.

I used strtok(), but it stops processing after the first null.

my code is below.
-------------------------------------------------

% cd /proc/14007
% cat cmdline
emacs--background-colorblack/tmp/abc

---------------------------

% ps -e -o pid,args | grep 14007
14007 emacs --background-color black /tmp/abc

---------------------------------------

% a.out /proc/14007/cmdline
file length is: 0
content is [emacs] <<<<<----- everything after first null character is not shown
strlen: 5
1: emacs
Tokenizing complete


==============================================================
Code:
#include <stdio.h>


main (int argc, char *argv[])
{
  FILE *fp;
  char *tok;
  int x = 1;
                  
  long  lFileLen;               /* Length of file */
  char *contents;                  /* Dynamically allocated buffer (entire file) */

  if (argc < 2) {
     printf("need a filename\n");
     exit(1);
  }

  fp = fopen(argv[1], "r"); /* Open in BINARY mode */
  if (fp == NULL) {
      printf("could not open file\n");
      exit(2);
  }

  fseek(fp, 0L, SEEK_END);  /* Position to end of file */
  lFileLen = ftell(fp);     /* Get file length */
  rewind(fp);               /* Back to start of file */

  printf("file length is: %ld\n", lFileLen);
 
  lFileLen = 200; /* assume there are 200 bytes at most */
  
  contents = (char*)calloc(lFileLen + 1, sizeof(char));

  if(contents == NULL )
  {
    printf("\nInsufficient memory to read file.\n");
    return 0;
  }

  /* Read the entire file into contents */
  fread(contents, lFileLen, 1, fp); 
  
  fclose(fp);

  printf("content is [%s]\n", contents);  /* nothing after first null character !!! */
  printf("strlen: %d\n", strlen(contents)); 
  
   /* extract first string from string sequence */
  tok = (char*)strtok(contents, "\0");

  /* print first string after tokenized */
  printf("%i: %s\n", x, tok);

  /* loop until finishied */
  while (1) 
  { 
          /* extract string from string sequence */
          tok = (char*)strtok(NULL, "\0");

          /* check if there is nothing else to extract */
          if (tok == NULL)
          {
                  printf("Tokenizing complete\n");
               /*   exit(0); */
                  break;
          } 

          /* print string after tokenized */
          printf("/%i: %s\n", x, tok);
          x++;
  } 


  free(contents);

}

Last edited by Andrewkl; 10-29-2008 at 01:40 AM..
 

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LEARN ABOUT X11R4

resize

RESIZE(1)						      General Commands Manual							 RESIZE(1)

NAME

       resize - set TERMCAP and terminal settings to current xterm window size

SYNOPSIS

       resize [ -u | -c ] [ -s [ row col ] ]

DESCRIPTION

       Resize  prints  a  shell  command  for setting the TERM and TERMCAP environment variables to indicate the current size of xterm window from
       which the command is run.  For this output to take effect, resize must either be evaluated as part of the command line (usually done with a
       shell alias or function) or else redirected to a file which can then be read in.  From the C shell (usually known as /bin/csh), the follow-
       ing alias could be defined in the user's .cshrc:

	       %  alias rs 'set noglob; eval `resize`'

       After resizing the window, the user would type:

	       %  rs

       Users of versions of the Bourne shell (usually known as /bin/sh) that don't have command functions will need to send the output to a tempo-
       rary file and the read it back in with the ``.'' command:

	       $  resize > /tmp/out
	       $  . /tmp/out

OPTIONS

       The following options may be used with resize:

       -u      This option indicates that Bourne shell commands should be generated even if the user's current shell isn't /bin/sh.

       -c      This option indicates that C shell commands should be generated even if the user's current shell isn't /bin/csh.

       -s [rows columns]
	       This  option  indicates	that Sun console escape sequences will be used instead of the VT100-style xterm escape codes.  If rows and
	       columns are given, resize will ask the xterm to resize itself.  However, the window manager may choose to disallow the change.

	       Note that the Sun console escape sequences are recognized by XFree86 xterm and by dtterm.  The resize program may be  installed	as
	       sunsize, which causes makes it assume the -s option.

	       The  rows  and  columns	arguments  must appear last; though they are normally associated with the -s option, they are parsed sepa-
	       rately.

FILES

       /etc/termcap   for the base termcap entry to modify.

       ~/.cshrc       user's alias for the command.

SEE ALSO

       csh(1), tset(1), xterm(1)

AUTHORS

       Mark Vandevoorde (MIT-Athena), Edward Moy (Berkeley)
       Copyright (c) 1984, 1985 by X Consortium
       See X() for a complete copyright notice.

								  X Window System							 RESIZE(1)
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