This project is all about trying to create a Bash Terminal using System Programming.

Functions added

-cat command
-change directory
-list command
-make new directory
-print current working directory
-remove directory

Implementation

cat command

The names of the file(s) to be read is got as input and passed to void cat() function. The file is opened using "r" mode and the contents of the file are stored in a buffer s. The size of the buffer is chosen to be 1024, because 1024 is physical block size. Buffer size with a multiple of block size gives huge performance improvement than any other value, as most of the internal operations takes place interms of block size.

Arguments:

1. File name(s)

System Call used:`

1. fopen(const char *file_name, mode)
   fopen() opens the filename pointed in the respective mode (here in read mode)

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Change directory

Every directory has default . and . . folder. The . points to current directory and . . folder points to the previous parent directory. This helps us in moving to the parent directory.

Arguments:

1. const char* path_

System Call used:`

1. chdir(const char *path)
   Call to chdir() function changes the current working directory to the pathname specified by path

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list command

This command is used to list the directories, files (hidden) present inside the current directory.

Arguments:

1. string param
   to check if -a is used with ls command or not.
   If -a is present we print also need to hidden entries (files and directories), else print only normal entries.

System Call used:`

1. DIR dStream = opendir(const char dir);
   opendir() creates a directory stream representing the directory given. Directory stream is similar to a file descriptor, but represents a open directory, along with some meta data.

2. readdir(DIR *dStream)
   readdir() returns details of every file and folder(called entries) in the directory one by one. The return value is stored in a dirent structure.

    struct dirent {
        ino_t d_ino; 			 /* inode number */
    	off_t d_off; 			 /* offset to the next dirent */
    	unsigned short d_reclen; /* length of this record */
    	unsigned char d_type; 	 /* type of file */
    	char d_name[256]; 		 /* filename */
    };
   

run command

The applications can be opened from the terminal using the fork() and execv() system call. The fork() system call creates a new child process, followed by execv() system call which puts the process image/binary executable file into the process stack of child process and it gets running.