SHELL

find a substring from a string

// CPP program to demonstrate working of string
// find to search a string
#include <iostream>
#include <string>
  
using namespace std;
  
int main()
{
    string str = "geeksforgeeks a computer science";
    string str1 = "geeks";
  
    // Find first occurrence of "geeks"
    size_t found = str.find(str1);
    if (found != string::npos)
        cout << "First occurrence is " << found << endl;
  
    // Find next occurrence of "geeks". Note here we pass
    // "geeks" as C style string.
    char arr[] = "geeks";
    found = str.find(arr, found+1);
    if (found != string::npos)
        cout << "Next occurrence is " << found << endl;
  
    return 0;
}

search for substring

# You can do it in two ways
# 1) Let "grep" read on its standard input

echo "$line" | grep -o select

# 2) tell "grep" here is the string

grep select <<< "$line"