Using Chdir() In The C Programming Language, An Essay On Directory Manipulation.

On successful completion of the module, students will be able to:
1. Demonstrate critical awareness of the concepts and issues related to systems programming.
2. Design, implement, and evaluate programs employing aspects of systems programming.

Critical awareness of systems programming concepts and issues

On line five we parse two parameters argc and directory. The directory specifies the change location on line eight. If the change of directory happens successfully it returns the value of 0 while if it doesn’t it returns a value of -1. If it returns a value of -1 it means that there was an error while calling the system call function. While if it returns the value zero it means the calling of the system function was executed successfully.

Here, You don't change the directory, you just declare a function prototype for chdir in the program as stated above. You go ahead to compare that function pointer against zero which is a null value which return zero and makes the execution successful. Thus returning the directory stated above.

The string is to pass an the pointer to chdir(). chdir() requires a C Style string, which is  an array of characters parsed in argument terminated to change the current directory of the program running

You should note that in most operating system the current or working directory can only be set for the process itself and any children it creates in the system. It never affects the process that caused the process changing its current directory from where it was before the program of the system started

You can use the chdir() function call in the program, as stated in unistd.h.  With that it will change the working directory for the current process running in the system. The executable program running the c program. Although, it will not change directories the way we expect it to change. It will only change directories for the current process running in the system and exit the program when that is done. When the program exits the current working directory will return to what it was when the program was started running in the system. 

cd /usr 

This will change directories inside the script in the program to /usr directory, but if the script exits the working directory is remains the same again. You can't make a program to change directories in the shell directly, the shell can do this, which is why the cd command is built in to the Bash shell and not a independent program in the system structure.  You can use an alias or a shell function to make a command change directories under the shell in the system  

1. b) Returns the current working directory 

We specify the maximum length of the directory name to be stated as 80 on line 5. On line 1 and 2 we import the library headers for the c programming language. On line 7 we pass the arguments argc and directory on it. On line 13 we store the maximum

The string is to pass an the pointer to chdir(). chdir() requires a C Style string, which is  an array of characters parsed in argument terminated to change the current directory of the program running 

name on a variable named sizeOfBuffer. On line 15 we change to the current working directory. On line 20 and 21 we print print the current working directory as obtained from  getcwd() function on the users screen.

Design and implementation of programs with systems programming aspects

However you should note that in most operating system the current or working directory can only be set for the process itself and any children it creates in the system. It never affects the process that caused the process changing its current directory from where it was before the program of the system started.

You should not expect to find the working directory of your shell to be changed once your program ends. The working directory remains the same after the program comes to an end.

Here the values environment variables and the current working directory are propagated from the parent processes to child processes and not back to parent processes. If a child process in your program calls (chdir), sets or modifies an environment variable, that affects that process of all of its children, but cannot affect the parent  processes in the program.

The string is to pass an the pointer to chdir(). chdir() requires a C Style string, which is  an array of characters parsed in argument terminated to change the current directory of the program running

In conclusion chdir is  a built-in command in the shell of the system terminal or the command line meaning it can be implemented as a separate program. If you want to run a program that changes your shell current directory, you need to do a little of changes with the program.

 For instance, your program has the ability of printing cd command in the shell, and you can have that output in the shell.  With that you can combine the function to achieve such functionality in it. Finally, the program returns value of -1 indicating that an error occurred in the system call and it was unable to return the current working directory in the program. While when it returns value of 0 it indicates that system call functioned correctly as it was expected to do. 

The cd command is not built in to the shell , It is not something external and executable in the shell. If we use the external command to change it,that will not have any effect on the parent shell. And there is no command;

/bin/cd

/user/bin/cd 

In conclusion, when a shell executes any command, it does invoke folk() function letting the child processes to use exec() function on it to  execute the command entered by the user in the shell. For instance, if the command entered is “/ls”, the shell arranges and execute /bin/ls with two arguments on it that is ls and / current directory. The string is to pass an the pointer to chdir(). chdir() requires a C Style string, which is  an array of characters parsed in arg terminated to change the current directory of the program running. However, if we select the  command  chdir() for a system call, that affects the child process in the shell and not the parent processes in it. With that, the shell has to handle the “cd” command itself, not using folk() or exec() function calls .

Understanding the chdir() function call in the C programming language

Note that in DOS, a .BAT file can do a change directory command and it affects the cmd.exe in the shell. While in Unix this never happens - a child process do not affect the current directory of the parent process in the shell.

You can use the chdir() function call in the program, as stated in unistd.h.  With that it will change the working directory for the current process running in the system. The executable program running the c program. Although, it will not change directories the way we expect it to change. It will only change directories for the current process running in the system and exit the program when that is done. When the program exits the current working directory will return to what it was when the program was started running in the system.

cd /usr 

This will change directories inside the script in the program to /usr directory, but if the script exits the working directory is remains the same again. You can't make a program to change directories in the shell directly, the shell can do this, which is why the cd command is built in to the Bash shell and not a standalone program in the system structure.  You can use an alias or a shell function to make a command change directories under the shell in the system

Using the above stated code , you can modify the current shell with whatever exists in the script you're sourcing getting it from. Note that if you ran 'cd' directly in the shell, it would not work for the same problem you are already experiencing and works for that only specific problem there; you must call it with what is in the source. 

However exec*() functions are always at the lowest-level functions for executing processes in the program. The first argument makes the program to be run in the normal , a binary;  a script with a program line such as #!/bin/sh on the first line). This is a null-terminated list of the arguments to the program. If you want to execute the ls command with the option -l, then you always specify in the argument v argument the three values "ls", "-l" and a null pointer when running the program. 

You should note that in most operating system the current or working directory can only be set for the process itself and any children it creates in the system. It never affects the process that caused the process changing its current directory from where it was before the program of the system started.

You should not expect to find the working directory of your shell to be changed once your program ends. The working directory remains the same after the program comes to an end.

From line 10 to 15 the system call opens the directory specified in the parameter directory ready for calls to

read the directory specified in the command.

On line 15 the directory could be opened, opendir returns a unique directory descriptor which is a non-

Effects of using chdir() on the current working directory

zero integer. If the system call fails, a value of 0 is returned in the program execution. 

From line 21 the system call reads the next directory entry from the directory previously opened by a call

to opendir. The first parameter is the directory descriptor returned by opendir. The second

parameter is a pointer to a caller-supplied buffer that will be filled with the contents of the

_DirectoryEntry structure that is provided in fs.h. 

On line 25 the system call closes the directory previously opened by a call to opendir.

A return value of 0 indicates that the system call functioned correctly in the program. A value of -1 indicates

that an error occurred while executing the program. 

This will change directories inside the script in the program to /usr directory, but if the script exits the working directory is remains the same again. You can't make a program to change directories in the shell directly, the shell can do this, which is why the cd command is built in to the Bash shell and not a standalone program in the system structure.  You can use an alias or a shell function to make a command change directories under the shell in the system 

We parse parameters to the function in c programming language. One of the parameters being the maximum size of the name of the directory to be given. Second one being the structure  of the directory pointer in c programming.  

The string is to pass an the pointer to chdir(). chdir() requires a C Style string, which is  an array of characters parsed in argument terminated to change the current directory of the program running

In conclusion chdir is  a built-in command in the shell of the system terminal or the command line meaning it can be implemented as a separate program. If you want to run a program that changes your shell current directory, you need to do a little of changes with the program.

 For instance, your program has the ability of printing cd command in the shell, and you can have that output in the shell.  With that you can combine the function to achieve such functionality in it. 

Implementation of ls.exe  

From line 9 we specify the dir where <dir> is the directory you want to list the contents of. If no directory is specified, then the

contents of the current directory should be listed in the specified directory. 

In line 13 you do not have to list the contents of that root

directory. It is also acceptable for you to only list the contents of a sub-directory in where it is specified in the program or just list the contents of that directory. 

The string passes an the pointer to chdir(). chdir() requires a C Style string, which is  an array of characters parsed in arg terminated to change the current directory of the program running 

Here again you just need  to list the names of files and the directories specified in the program. 

Differences between changing directories in the shell and in a C program

You should note that in most operating system the current or working directory can only be set for the process itself and any children it creates in the system. It never affects the process that caused the process changing its current directory from where it was before the program of the system started.

You should not expect to find the working directory of your shell to be changed once your program ends. The working directory remains the same after the program comes to an end. 

This will change directories inside the script in the program to /usr directory, but if the script exits the working directory is remains the same again. You can't make a program to change directories in the shell directly, the shell can do this, which is why the cd command is built in to the Bash shell and not a standalone program in the system structure.  You can use an alias or a shell function to make a command change 

The execvp() will always search for ls on  $PATH and execute the first program found that matches the ls command. The second will execute /bin/ls without looking at $PATH at all as it has not to check on that path.

Suppose argv[0] contain ls -l command, then there is a problem. Most operating systems do not have a file /bin/ls-l or /user/bin/ls-al where the blank is part of the name to be executed, but that's what we are  seeking to execute in the program

ns are always at the lowest-level functions for executing processes in the program. The first argument makes the program to be run in the normal , a binary;  a script with a program line such as #!/bin/sh on the first line). This is a null-terminated list of the arguments to the program. If you want to execute the ls command with the option -l, then you always specify in the argument v argument the three values "ls", "-l" and a null pointer when running the program.

From line 9 to 12 we specify the directory where <dir> is the directory you want to list the contents of. If no directory is specified, then the

contents of the current directory should be listed in the specified directory.

In line 13 and 14  you do not have to list the contents of that root

directory. It is also acceptable for you to only list the contents of a sub-directory in where it is specified in the program or just list the contents of that directory.

Here again you just need  to list the names of files and the directories specified in the program.

When you reach the final part of the directory in the system, it turns to another value that goes to the end of execution of a program. You can't make a program to change directories in the shell directly, the shell can do this, which is why the cd command is built in to the Bash shell and not a independent program in the system structure.  You can use an alias or a shell function to make a command change directories under the shell in the system

Conclusion

In conclusion, running commands on the c program doesn’t invoke the parent shell to change it’s directory.In system programming, you can use the chdir() function call in the program, as stated in unistd.h.  With that it will change the working directory for the current process running in the system. The executable program running the c program. Although, it will not change directories the way we expect it to change. It will only change directories for the current process running in the system and exit the program when that is done. When the program exits the current working directory will return to what it was when the program was started running in the system (Reda, Tawfik, Marzok, & Khamis, 2015)).

cd /usr 

This will change directories inside the script in the program to /usr directory, but if the script exits the working directory is remains the same again. You can't make a program to change directories in the shell directly, the shell can do this, which is why the cd command is built in to the Bash shell and not a independent program in the system structure.  You can use an alias or a shell function to make a command change directories under the shell in the system. However exec*() functions are always at the lowest-level functions for executing processes in the program. The first argument makes the program to be run in the normal , a binary;  a script with a program line such as #!/bin/sh on the first line). This is a null-terminated list of the arguments to the program. If you want to execute the ls command with the option -l, then you always specify in the argument v argument the three values "ls", "-l" and a null pointer when running the program.

References

Reda, N. M., Tawfik, A., Marzok, M. A., & Khamis, S. M. (2015).Sort-Mid tasks scheduling algorithm in grid computing. Journal of advanced research, 6(6), 987-993. Zhou, X., & Curry, W. (2015). U.S. Patent No. 8,971,927. Washington, DC: U.S. Patent and Trademark Office.

Yigit, M., Gungor, V. C., Fadel, E., Nassef, L., Akkari, N., & Akyildiz, I. F. (2016). Channel-aware routing and priority-aware multi-channel scheduling for WSN-based smart grid applications. Journal of Network and Computer Applications, 71, 50-58.

Zhou, X., & Curry, W. (2015). U.S. Patent No. 8,971,927. Washington, DC: U.S. Patent and Trademark Office.