CYCLE-1
S. No LIST OF EXPERIMENTS
Exp-1 Practicing of Basic UNIX Commands.
Exp-2 Write programs using the following UNIX operating system calls
fork, exec, getpid, exit, wait, close, stat, opendir and readdir
Exp-3 Simulate UNIX commands like cp, ls, grep, etc.,
Basic Unix Commands
Getting help in Unix
man – view manual pages for Unix commands
Unix Shell Commands
clear – clear screen
history – show history of previous commands
Time and Date commands
date – show current date and time
sleep – wait for a given number of seconds
uptime – find out how long the system has been up
Unix users commands
These commands allow you to get basic information about Unix users in your
environment.
whoami – show your username
id – print user identity
groups – show which groups user belongs to
passwd – change user password
who – find out who is logged into the system
last – show history of logins into the system
Unix file operations
Navigating filesystem and managing files and access permissions:
ls – list files and directories
cp – copy files (work in progress)
rm – remove files and directories (work in progress)
mv – move or rename files and directories to another location
chmod – change file/directory access permissions
chown – change file/directory ownership
Text file operations in Unix
Most of important configuration in Unix is in clear text files, these commands will let you
quickly inspect files or view logs:
cat – concatenate files and show contents to the standard output
more – basic pagination when viewing text files or parsing Unix commands output
less – an improved pagination tool for viewing text files (better than more command)
head – show the first 10 lines of text file (you can specify any number of lines)
tail – show the last 10 lines of text file (any number can be specified)
grep – search for patterns in text files
Unix directory management commands
Navigating filesystems and managing directories:
cd – change directory
pwd – confirm current directory
ln – make links and symlinks to files and directories
mkdir – make new directory
rmdir – remove directories in Unix
Unix system status commands
Most useful commands for reviewing hostname configuration and vital stats:
hostname – show or set server hostname
w – display system load, who’s logged in and what they are doing
uname – print Unix system information
Reboot
shutdown – graceful shutdown and reboot of your system
halt – ungraceful (without stopping OS services) shutdown
reboot – ungraceful reboot (without stopping OS services)
Networking commands in Unix
Most useful commands for inspecting network setup and exploring network connections and
ports:
ifconfig – show and set IP addresses (found almost everywhere)
ip – show and set IP addresses (in recent Linux versions)
ping – check if remote host is reachable via ICMP ping
netstat – show network stats and routing information
Process management
Listing processes and confirming their status, and stopping processes if needed:
ps – list processes
top – show tasks and system status (check out htop as well)
kill – kill a process (stop application running)
Remote access commands
ssh is really the only way to go, but it’s important to know telnet as well:
telnet – clear-text (insecure) remote access protocol
ssh – Secure SHell – encrypted remote access client
o check out the SSH reference!
File transfers commands
Always useful to know how to copy files between servers or just download some package
from the web:
ftp – clear-text (insecure!) File Transfer Protocol client
sftp – secure (encrypted) version of FTP
scp – secure (encrypted) version of cp command
wget – download files from remote servers, HTTP/HTTPS and FTP
curl – download files from remote servers, HTTP/HTTPS and FTP
1.File and Directory Management
1. pwd
o Prints the current working directory.
o Example:
bash
Copy code
pwd
2. ls
o Lists files and directories in the current directory.
o Options:
-l: Long format (permissions, owner, size, etc.).
-a: Includes hidden files.
o Example:
bash
Copy code
ls -la
3. cd
o Changes the directory.
o Example:
bash
Copy code
cd /path/to/directory
4. mkdir
o Creates a new directory.
o Example:
bash
Copy code
mkdir new_directory
5. rmdir
o Removes an empty directory.
o Example:
bash
Copy code
rmdir empty_directory
6. touch
o Creates an empty file.
o Example:
bash
Copy code
touch file.txt
7. rm
o Removes files or directories.
o Options:
-r: Recursively delete directories.
o Example:
bash
Copy code
rm file.txt
rm -r directory_name
8. cp
o Copies files or directories.
o Example:
bash
Copy code
cp file.txt /path/to/destination
9. mv
o Moves or renames files or directories.
o Example:
bash
Copy code
mv file.txt /path/to/destination
mv old_name.txt new_name.txt
File Viewing
1. cat
o Displays the contents of a file.
o Example:
bash
Copy code
cat file.txt
2. less
o Allows scrolling through a file's contents.
o Example:
bash
Copy code
less file.txt
3. head
o Displays the first few lines of a file.
o Example:
bash
Copy code
head file.txt
4. tail
o Displays the last few lines of a file.
o Example:
bash
Copy code
tail file.txt
5. nano, vim, or vi
o Opens text editors directly from the command line.
File Permissions
1. chmod
o Changes file permissions.
o Example:
bash
Copy code
chmod 755 script.sh
2. chown
o Changes file ownership.
o Example:
bash
Copy code
chown user:group file.txt
Process Management
1. ps
o Lists running processes.
o Example:
bash
Copy code
ps aux
2. kill
o Terminates a process by its PID.
o Example:
bash
Copy code
kill 12345
3. top
o Displays real-time system usage and processes.
o Example:
bash
Copy code
top
Networking
1. ping
o Tests connectivity to a host.
o Example:
bash
Copy code
ping google.com
2. ifconfig or ip a
o Displays network interface information.
o Example:
bash
Copy code
ip a
Searching
1. find
o Searches for files in a directory hierarchy.
o Example:
bash
Copy code
find /path/to/search -name "file.txt"
2. grep
o Searches for patterns in files.
o Example:
bash
Copy code
grep "search_term" file.txt
System Information
1. uname
o Displays system information.
o Example:
bash
Copy code
uname -a
2. df
o Displays disk space usage.
o Example:
bash
Copy code
df -h
3. du
o Displays disk usage for files and directories.
o Example:
bash
Copy code
du -sh /path/to/directory
4. whoami
o Displays the current user.
o Example:
bash
Copy code
whoami
Practice Tips
Use a sandbox or virtual machine to practice without risking your main system.
Try combining commands with pipes (|) to perform complex tasks.
Example:
bash
Copy code
ls -l | grep "filename"
2.1. fork and getpid
A program to create a child process and display process IDs.
c
Copy code
#include <stdio.h>
#include <unistd.h>
int main() {
pid_t pid = fork(); // Create a child process
if (pid < 0) {
perror("Fork failed");
} else if (pid == 0) {
printf("Child process: PID = %d\n", getpid());
} else {
printf("Parent process: PID = %d, Child PID = %d\n", getpid(), pid);
}
return 0;
}
2. exec
A program to replace the current process with a new one.
c
Copy code
#include <stdio.h>
#include <unistd.h>
int main() {
printf("Executing `ls` command:\n");
execl("/bin/ls", "ls", "-l", (char *)NULL); // Replace current process with `ls`
perror("execl failed");
return 1;
}
3. exit and wait
A program where the child exits and the parent waits.
c
Copy code
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
int main() {
pid_t pid = fork();
if (pid < 0) {
perror("Fork failed");
} else if (pid == 0) {
printf("Child process exiting with code 42\n");
exit(42); // Exit with a status code
} else {
int status;
wait(&status); // Parent waits for the child
if (WIFEXITED(status)) {
printf("Child exited with status: %d\n", WEXITSTATUS(status));
}
}
return 0;
}
4. close
A program to open, write to, and close a file descriptor.
c
Copy code
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
int main() {
int fd = open("example.txt", O_CREAT | O_WRONLY, 0644);
if (fd < 0) {
perror("Open failed");
return 1;
}
write(fd, "Hello, UNIX!\n", 13); // Write to the file
close(fd); // Close the file descriptor
printf("File written and closed successfully.\n");
return 0;
}
5. stat
A program to retrieve and display file information.
c
Copy code
#include <stdio.h>
#include <sys/stat.h>
int main() {
struct stat fileStat;
if (stat("example.txt", &fileStat) < 0) {
perror("stat failed");
return 1;
}
printf("File Size: %ld bytes\n", fileStat.st_size);
printf("File Permissions: %o\n", fileStat.st_mode & 0777);
printf("Last Access Time: %ld\n", fileStat.st_atime);
return 0;
}
6. opendir and readdir
A program to list all files in a directory.
c
Copy code
#include <stdio.h>
#include <dirent.h>
int main() {
DIR *dir = opendir(".");
if (dir == NULL) {
perror("opendir failed");
return 1;
}
struct dirent *entry;
printf("Files in current directory:\n");
while ((entry = readdir(dir)) != NULL) {
printf("%s\n", entry->d_name);
}
closedir(dir); // Close the directory stream
return 0;
}
Compilation and Execution
1. Save the code to a file, e.g., program.c.
2. Compile with gcc:
bash
Copy code
gcc program.c -o program
3. Run the program:
bash
Copy code
./program
Let me know if you need additional explanations or variations of these examples!
4o
3.
1. Simulate cp (Copy File)
c
Copy code
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char *argv[]) {
if (argc != 3) {
printf("Usage: %s <source_file> <destination_file>\n", argv[0]);
return 1;
}
int src = open(argv[1], O_RDONLY);
if (src < 0) {
perror("Source file open failed");
return 1;
}
int dest = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
if (dest < 0) {
perror("Destination file open failed");
close(src);
return 1;
}
char buffer[1024];
ssize_t bytesRead, bytesWritten;
while ((bytesRead = read(src, buffer, sizeof(buffer))) > 0) {
bytesWritten = write(dest, buffer, bytesRead);
if (bytesWritten != bytesRead) {
perror("Write error");
close(src);
close(dest);
return 1;
}
}
close(src);
close(dest);
printf("File copied successfully.\n");
return 0;
}
2. Simulate ls (List Files in Directory)
c
Copy code
#include <stdio.h>
#include <dirent.h>
int main(int argc, char *argv[]) {
const char *path = (argc == 2) ? argv[1] : ".";
DIR *dir = opendir(path);
if (dir == NULL) {
perror("Failed to open directory");
return 1;
}
struct dirent *entry;
while ((entry = readdir(dir)) != NULL) {
printf("%s\n", entry->d_name);
}
closedir(dir);
return 0;
}
3. Simulate grep (Search for Pattern in File)
c
Copy code
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[]) {
if (argc != 3) {
printf("Usage: %s <pattern> <file>\n", argv[0]);
return 1;
}
const char *pattern = argv[1];
const char *filename = argv[2];
FILE *file = fopen(filename, "r");
if (file == NULL) {
perror("File open failed");
return 1;
}
char line[1024];
while (fgets(line, sizeof(line), file)) {
if (strstr(line, pattern)) { // Check if pattern exists in the line
printf("%s", line);
}
}
fclose(file);
return 0;
}
Compilation and Execution
1. Save the programs to files, e.g., cp_sim.c, ls_sim.c, and grep_sim.c.
2. Compile using gcc:
bash
Copy code
gcc cp_sim.c -o cp_sim
gcc ls_sim.c -o ls_sim
gcc grep_sim.c -o grep_sim
3. Run the programs:
o For cp:
bash
Copy code
./cp_sim source.txt destination.txt
o For ls:
bash
Copy code
./ls_sim /path/to/directory
o For grep:
bash
Copy code
./grep_sim pattern file.txt
These simple programs mimic the basic functionality of the respective UNIX commands.
You can extend them by adding more options and error handling for a closer simulation of
the real commands. Let me know if you need any further assistance!
4o
