awk: Statements(2)

1. Iterative Statements: for(2)
text2:

 2 Chicago  
 1 Boston  
 3 Atlanta  

script_1:
i  will iterate the index of all cities.

 #! /bin/bash  
   
 awk '{ cities[$1] = $2; }  
    END {  
    for ( i in cities )  
    {  
      print i ":" cities[i];  
    }}' text2  

terminal:

 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ ./script_1  
 1:Boston  
 2:Chicago  
 3:Atlanta  

2. Iterative Statements: for(3)
text2 is same as above

script_1:
"break" is getting out of current loop, "continue" is going to next iteration of the loop and skipping remaining operations.

 #! /bin/bash  
   
 awk '{ cities[$1] = $2; }  
    END {  
    for ( i in cities )  
    {  
      if (i==2)  
        break;  
      print i ":" cities[i];  
    }  
      
    print "";  
   
    for (i in cities)  
    {  
      if (i==1)  
        continue;  
      print i ":" cities[i];  
    }  
 }' text2  

terminal:

 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ ./script_1  
 1:Boston  
   
 2:Chicago  
 3:Atlanta  

3. Iterative Statements: while
text2:

 Hello Chicago  
 Hello Boston  
   

script_1:

 #! /bin/bash  
   
 awk '{  
   i=0;  
   while(i<=NF)  
   {  
     print $i;  
     i++;  
   }  
 }' text2  

terminal:
while loop is checking the condition before each iteration, if true, continue to run.The last empty line is for the last empty line in "text2". awk is still taking that as one record.

 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ ./script_1  
 Hello Chicago  
 Hello  
 Chicago  
 Hello Boston  
 Hello  
 Boston