 /* (2)
Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It
accepts the command, tokenize the command line and execute it by creating the child process.
Also implement the additional command ‘search’ as
myshell$ search f filename pattern : It will search the first occurrence of pattern in the given
file
myshell$ search a filename pattern : It will search all the occurrence of pattern in the given file
myshell$ search c filename pattern : It will count the number of occurrence of pattern in the
given file*/

#include<stdio.h>
#include<string.h>


int main()
{
  int i,j,pid,pid2,count=0,cnt,pos;
    
  FILE *fp1,*fp2;
  char token[100]={'\0'},str[100],str1[100],str2[10]={'\0'},ch,command[100]={'\0'},argument1[100]={'\0'},argument2[100]={'\0'},argument3[100]={'\0'};
  
  
  printf("\n Welcome to Command Prompt");
  

  
   while(1)
   {
    printf("\n[ myshell $ ]");
    gets(str);
    //printf("%s",str);
    i=0;
    j=0;
    count=0;
    while(str[i]!='\0')
    {
       j=0;
       count++;
      while(str[i]!=' ')
      {
         
         token[j]=str[i];
          i++;
          j++;
      }
      token[j]='\0';
      //printf("\n %s",token);
      if(count==1)
      {
        strcpy(command,token);
        
      }
      else if(count==2)
      {
        strcpy(argument1,token);
        // printf("\n %s",argument1);
      }
      else if(count==3)
      {
        strcpy(argument2, token);
        //printf("%s",argument2);
      }
      else
      {
        strcpy(argument3,token);
        printf("%s",argument3);
      }
      i++;
      
    }
    
    pid=fork();
    
      
      if(strcmp(command,"search")==0)
      {
        
        
            if(strcmp(argument1,"f")==0)
            {
              fp1=fopen(argument2,"r");
              if(fp1==NULL)
              {
                printf("\n Error in opening the file ");
                break;
              
              }
              else
              {
                cnt=1;
              while(!feof(fp1))
              {
                fscanf(fp1,"%s",&str1);
                if(strcmp(str1,argument3)==0)
                {
                  printf("First Occurence of pattern %s is at line %d",str1,cnt);
                  cnt++;
                  break;
                }
                
              }
              if(cnt==1)
              {
                printf("\n This pattern is not found ");
              }
              }
              break;
            }
            
            
      
      
        
  }
}
}

created 1 year ago by Chaitrali Chinchanikar

C Language online compiler

Write, Run & Share C Language code online using OneCompiler's C online compiler for free. It's one of the robust, feature-rich online compilers for C language, running the latest C version which is C18. Getting started with the OneCompiler's C editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'C' and start coding!

Read inputs from stdin

OneCompiler's C online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample C program which takes name as input and print your name with hello.

#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

Structured Programming
Popular system programming language
UNIX, MySQL and Oracle are completely written in C.
Supports variety of platforms
Efficient and also handle low-level activities.
As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}