I currently got the task of programming a UNIX Shell for practice. The functionality is as follows:
1. Entering commands with the keyboard. Enter stops the input and creates a process which should start any program
2. the shell waits for termination of each command before another command can be accepted
3. parameters should be extracted and correctly delivered to the specific programm
4. "logout" ends the shell (more of that later)
5. commands which have an '&' appended should be executed in the background. new commands can be entered thereafter
-> commands are not to be hardcoded
6. entering CTRL-C should deliver the currently running foreground process the signal SIGINT (not the shell)
7. entering CTRL-Z should deliver the currently running foregruond process the signal SIGSTP
8. implement a command "fg" that brings back a process back to the foreground which has been stopped by CTRL-Z
9. implement a command "bg" that lets a stopped process (by CTRL-Z) run again in the background
10. the shell can only be terminated if all background processes have been terminated, else give an error message, and make sure there should not be any zombie processes
I already started doing some of the tasks but I'm terribly unsure of how to exactly handle processes, it's very new to me. I would be delighted if someone could give me a more or less simple solution, so I can get the picture of it.
My code so far:
Code:
#include <cstdlib>
#include <iostream>
#include <string>
#include <time.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <vector>
using namespace std;
void getArguments();
string input="";
vector<char*> arguments;
int main(int argc, char** argv) {
cout << "Welcome to my shell. Exit with “logout“.0" << endl;
while (input!= "logout") {
getline(cin, input);
//getArguments();
size_t space = input.find(" ");
string command= input.substr(0,space);
int end = input.length() - space;
string text = input.substr(space+1, ende);
string path = "/usr/bin/" + command;
pid_t pid = fork();
if(pid == 0)
{
cout << "Process " << command << " wird ausgeführt: \n";
execlp(path.c_str(), NULL);
}
if(text!="&")
waitpid(pid, 0, 0);
}
return 0;
}
Hi all,
Can anyone provide me any checklists or a list of steps I should follow before executing my scripts.
Could also tell me if there are any other standards to be followed while shell programming like naming conventions for variables etc.
Your help would be much appreciated.
Regards,... (2 Replies)
Hi,
Iam using split command to split the files.
Splitted files will be named as xaa
xab
xac
xad etc.
Directories will be test1,test2,test3.....
Now i want to select the splitted files one by one and have to place in test directories.
can anybody give the soulution??? (2 Replies)
Hi,
i want to read a full file.
If i want to split the file and by reading parralel each, i can save the time.
Can any body give me the suggesion??
ia m using this function to read a file and using that i have to grep in another file. since the file 1 is huge it is taking lot of time.
... (3 Replies)
Hi,
I am looking for a PDF or an e-book which can show in details how to do Shell Scripting or Programming. Can anybody provide me with a link to such a tutorial? I have downloaded some tutorials but they show only basics and not give any in-depth study material.
I am using Red Hat Linux... (2 Replies)
Hi Gurus
I am very new to Unix Shell Prog. I have a file in format
Q1 Dirname-FileName Score Remarks
i.e. containing columns separated by space. I want to read Column 1 and 2 and then join them to make a string that would be a path to a file. I will use this string to fetch the files and... (4 Replies)
Hi guys
i have two different line
input
M5.7&a : M5 minimum density is 20%, maximum density is 80%,
DENSITY PERM=M5.8&a(180) ......... 6 violations found.
M6.7&a : M6 minimum density is 20%, maximum density is 80%,
DENSITY A=M6.8&a(180) ......... 6 violations found.
need... (2 Replies)
Guys,
What do you think is the best way to learn UNIX and shell scripting?
** I keep on searching tutorials online, where I loose most of my time :(
Let me know the way you learnt the UNIX concepts, your replies might help me learn more.
Thanks a ton:b: (2 Replies)
1. The problem statement, all variables and given/known data:
Hello! :)
I currently got the task of programming a UNIX Shell for practice. The functionality is as follows:
1. Entering commands with the keyboard. Enter stops the input and creates a process which should start any program
2.... (0 Replies)
Discussion started by: DarkDan
0 Replies
LEARN ABOUT OPENSOLARIS
wait
wait(1) User Commands wait(1)NAME
wait - await process completion
SYNOPSIS
/bin/sh
wait [pid]...
/bin/jsh /bin/ksh /usr/xpg4/bin/sh
wait [pid]...
wait [% jobid...]
/bin/csh
wait
ksh93
wait [job...]
DESCRIPTION
The shell itself executes wait, without creating a new process. If you get the error message cannot fork,too many processes, try using the
wait command to clean up your background processes. If this doesn't help, the system process table is probably full or you have too many
active foreground processes. There is a limit to the number of process IDs associated with your login, and to the number the system can
keep track of.
Not all the processes of a pipeline with three or more stages are children of the shell, and thus cannot be waited for.
/bin/sh, /bin/jsh
Wait for your background process whose process ID is pid and report its termination status. If pid is omitted, all your shell's currently
active background processes are waited for and the return code is 0. The wait utility accepts a job identifier, when Job Control is enabled
(jsh), and the argument, jobid, is preceded by a percent sign (%).
If pid is not an active process ID, the wait utility returns immediately and the return code is 0.
csh
Wait for your background processes.
ksh
When an asynchronous list is started by the shell, the process ID of the last command in each element of the asynchronous list becomes
known in the current shell execution environment.
If the wait utility is invoked with no operands, it waits until all process IDs known to the invoking shell have terminated and exit with
an exit status of 0.
If one or more pid or jobid operands are specified that represent known process IDs (or jobids), the wait utility waits until all of them
have terminated. If one or more pid or jobid operands are specified that represent unknown process IDs (or jobids), wait treats them as if
they were known process IDs (or jobids) that exited with exit status 127. The exit status returned by the wait utility is the exit status
of the process requested by the last pid or jobid operand.
The known process IDs are applicable only for invocations of wait in the current shell execution environment.
ksh93
wait with no operands, waits until all jobs known to the invoking shell have terminated. If one or more job operands are specified, wait
waits until all of them have completed. Each job can be specified as one of the following:
number number refers to a process ID.
-number number refers to a process group ID.
%number number refers to a job number
%string Refers to a job whose name begins with string
%?string Refers to a job whose name contains string
%+ Refers to the current job
%%
%- Refers to the previous job
If one ore more job operands is a process id or process group id not known by the current shell environment, wait treats each of them as if
it were a process that exited with status 127.
OPERANDS
The following operands are supported:
pid The unsigned decimal integer process ID of a command, for which the utility is to wait for the termination.
jobid A job control job ID that identifies a background process group to be waited for. The job control job ID notation is applicable
only for invocations of wait in the current shell execution environment, and only on systems supporting the job control option.
USAGE
On most implementations, wait is a shell built-in. If it is called in a subshell or separate utility execution environment, such as one of
the following,
(wait)
nohup wait ...
find . -exec wait ... ;
it returns immediately because there is no known process IDs to wait for in those environments.
EXAMPLES
Example 1 Using A Script To Identify The Termination Signal
Although the exact value used when a process is terminated by a signal is unspecified, if it is known that a signal terminated a process, a
script can still reliably figure out which signal is using kill, as shown by the following (/bin/ksh and /usr/xpg4/bin/sh):
sleep 1000&
pid=$!
kill -kill $pid
wait $pid
echo $pid was terminated by a SIG$(kill -l $(($?-128))) signal.
Example 2 Returning The Exit Status Of A Process
If the following sequence of commands is run in less than 31 seconds (/bin/ksh and /usr/xpg4/bin/sh):
sleep 257 | sleep 31 &
jobs -l %%
then either of the following commands returns the exit status of the second sleep in the pipeline:
wait <pid of sleep 31>
wait %%
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of wait: LANG, LC_ALL, LC_CTYPE, LC_MES-
SAGES, and NLSPATH.
EXIT STATUS
ksh93
The following exit values are returned by the wait built-in in ksh93:
0 wait was invoked with no operands. All processes known by the invoking process have terminated.
127 job is a process id or process group id that is unknown to the current shell environment.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
|Interface Stability |Committed |
+-----------------------------+-----------------------------+
|Standard |See standards(5). |
+-----------------------------+-----------------------------+
SEE ALSO csh(1), jobs(1), ksh(1), ksh93(1), sh(1), attributes(5), environ(5), standards(5)SunOS 5.11 13 Mar 2008 wait(1)