Using C language to use system calls Post: 302734115

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Homework and Emergencies Homework & Coursework Questions Using C language to use system calls Post 302734115 by Corona688 on Wednesday 21st of November 2012 03:53:45 PM

11-21-2012

Registered User

It's possible to do it either way. Line-by-line is probably easier.

Your using scanf incorrectly every time you use it. You can't store a string in a char, since a string is a char array, and you shouldn't be using scanf to read raw data. Read lines then feed them into sscanf, or your code may get stuck in infinite loops whenever the user types something wrong.

I'd do this:

Code:

while(1)
{
        char buf[512];
        int selection;
        if(fgets(buf, 512, stdin) == NULL) break; // Read line, quit on error
        // Convert line into number
        if(sscanf(buf, "%d", &selection) != 1)
        {
                fprintf(stderr, "you did not type a number\n");
                continue;
        }

        switch(selection)
        {
...
        }
}

Also, you cannot store an entire string inside a single character. You'll need to feed sscanf an array for the filenames. Something like this:

Code:

char fname[512];
printf("Please enter a filename:\n");
// Read a line
fgets(fname, 512, stdin);
// chop the newline off the end of the line
for(n=0; fname[n]; n++) if(fname[n] == '\n') fname[n]='\0';

System calls you'll need are unlink to remove files, open to read or create files, read to read from files, write to write to files, and close to close file descriptors once you're done.

Include files you'll need for all those are

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

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sysman_menu

sysman_menu(8)						      System Manager's Manual						    sysman_menu(8)

NAME

       sysman_menu - Graphical interface to run system management tasks

SYNOPSIS

       /usr/sbin/sysman [-ui cui | gui] [-display displayname] [-menu]

       /usr/sbin/sysman [-accel] <accelerator> [arguments]

       /usr/sbin/sysman [-menu] <name> [arguments]

       /usr/sbin/sysman [-menu] -list

       /usr/sbin/sysman [-menu] -help  | -h

       /usr/sbin/sysman -focus hostname

OPTIONS

       Specifies the user interface to be invoked. The choices are: Specifies command line interface.  Specifies graphical user interface.  Speci-
       fies the display screen on where sysman_menu displays its window. If the display option is not  specified,  sysman_menu	uses  the  display
       screen  specified by your DISPLAY environment variable. The display option has the format hostname:server.number. The default is :0.0.  For
       more information, see the X(1X) reference page.	In a TruCluster environment, some management tasks effect the cluster as a whole and  some
       are  local  to  a specific cluster member.  If a task requires focus, the "Choose a host to manage" dialog box will be displayed. To launch
       the task directly, bypassing this dialog box, you can specify the -focus option.  Directly invokes the  task  with  that  accelerator.  Any
       arguments are passed on to the task itself. Use sysman -list for a list of the accelerators.

	      If  the  accelerator is for a branch of the menu and not an executable task, then the menu hierarchy is expanded to display the con-
	      tents of the specified branch.  Same as -accel option but the name of the task as displayed in the SysMan  Menu  is  specified.  For
	      example, sysman -menu "Manage local users". Any arguments are passed on to the task itself.

	      The  name is for a branch of the menu and not an executable task, then the menu hierarchy is expanded to display the contents of the
	      specified branch.  Displays a list of all the tasks that can be run from the SysMan Menu and their accelerators.	Displays help  for
	      the SysMan Menu.

DESCRIPTION

       SysMan Menu is used by the system administrator to obtain system management data and run selected system management tasks. SysMan Menu pro-
       vides a menu of system management tasks in a tree type display, with branches of management categories and leaves of actual tasks.  Select-
       ing a leaf or tasks invokes a task, which displays a dialog for performing the task.

       SysMan  Menu and its associated tasks can be run on an X Windows display, a terminal with curses capability, locally on a PC, or from a Web
       browser. For detailed information in running SysMan  Menu  from	a  PC  or  a  Web  browser,  please  use  your	Web  browser  and  go  to:
       http://your_machine_name:2301/SYSMAN/index.html.

       Online help is available for the SysMan Menu. To get help, select the Help button.

RESTRICTIONS

       You  must  have root privileges to perform most tasks with this application.  You can grant root privileges for specific users or groups of
       users using the Division of Privileges (DOP) application. See the dop(8) reference page and the online help in the sysman dopconfig  appli-
       cation for additional information.

       You must have the root privileges to execute some of the tasks on the SysMan Menu.

EXAMPLES

       The  following example shows how to launch the Manage local users task from the command line using an accelerator name: sysman -accel users
       The following example shows how to invoke SysMan Menu in curses mode: sysman -ui cui The following example shows how to get  a  listing	of
       tasks  and  their accelerators: sysman -list The following example, displays the status of the NFS related daemons on a remote cluster mem-
       ber: sysman -focus  nfs_config_status

SEE ALSO

       Commands: sysman_station(8), sysman_cli(8), sysman_clone(8), sysman(8)

       System Administration

       http://your_machine_name:2301/SYSMAN/index.html

																    sysman_menu(8)