Introduction
In this post, we are going to write a c program to find all the keywords in a file. Here, we are talking about the c keywords. So, there are 32 keywords in c programming. So, we will have to read any file which contains a c program. Our program will find all the keywords. This c program is also used to count the number of keywords in a file.
See the following input file which contains the c program.
Input File: abc.txt
int main()
{
int a,b,c;
float avg;
avg=(a+b+c)/3.0;
printf("Average = %0.2f", avg);
return 0;
}
Expected Output
The above file contains the c program. So, our program will read the above file i.e. abc.txt and our output will be
C Keywords are
int
int
float
return
Total Number of Keywords Are Found = 4Now, see the following program.
C Program to Find All The Keywords In a File
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *fp;
char ch;
char str[100];
int status=0,i=0, count=0;
fp=fopen("abc.txt","r");
if(fp==NULL)
{
printf("Error while opening a file");
return 0;
}
printf("C Keywords are \n");
while(fgets(str, sizeof(str), fp)!=NULL)
{
i=0;
while((ch=str[i])!='\0')
{
// for auto
if((ch=='a')&&(status==0))
{
status=1;
}
else if((ch=='u')&&(status==1))
{
status=2;
}
else if((ch=='t')&&(status==2))
{
status=3;
}
else if((ch=='o')&&(status==3))
{
printf("auto\n");
status=0;
count++;
}
// for break
else if((ch=='b')&&(status==0))
{
status=4;
}
else if((ch=='r')&&(status==4))
{
status=5;
}
else if((ch=='e')&&(status==5))
{
status=6;
}
else if((ch=='a')&&(status==6))
{
status=7;
}
else if((ch=='k')&&(status==7))
{
printf("break\n");
status=0;
count++;
}
// for case
else if((ch=='c')&&(status==0))
{
status=8;
}
else if((ch=='a')&&(status==8))
{
status=9;
}
else if((ch=='s')&&(status==9))
{
status=10;
}
else if((ch=='e')&&(status==10))
{
printf("case\n");
status=0;
count++;
}
// for case
else if((ch=='h')&&(status==8))
{
status=11;
}
else if((ch=='a')&&(status==11))
{
status=12;
}
else if((ch=='r')&&(status==12))
{
printf("char\n");
status=0;
count++;
}
// for const
else if((ch=='o')&&(status==8))
{
status=13;
}
else if((ch=='n')&&(status==13))
{
status=14;
}
else if((ch=='s')&&(status==14))
{
status=15;
}
else if((ch=='t')&&(status==15))
{
printf("const\n");
status=0;
count++;
}
// for continue
else if((ch=='t')&&(status==14))
{
status=16;
}
else if((ch=='i')&&(status==16))
{
status=17;
}
else if((ch=='n')&&(status==17))
{
status=18;
}
else if((ch=='u')&&(status==18))
{
status=19;
}
else if((ch=='e')&&(status==19))
{
printf("continue\n");
status=0;
count++;
}
// for default
else if((ch=='d')&&(status==0))
{
status=20;
}
else if((ch=='e')&&(status==20))
{
status=21;
}
else if((ch=='f')&&(status==21))
{
status=22;
}
else if((ch=='a')&&(status==22))
{
status=23;
}
else if((ch=='u')&&(status==23))
{
status=24;
}
else if((ch=='l')&&(status==24))
{
status=25;
}
else if((ch=='t')&&(status==25))
{
printf("default\n");
status=0;
count++;
}
// for double
else if((ch=='o')&&(status==20))
{
status=26;
}
else if((ch=='u')&&(status==26))
{
status=27;
}
else if((ch=='b')&&(status==27))
{
status=28;
}
else if((ch=='l')&&(status==28))
{
status=29;
}
else if((ch=='e')&&(status==29))
{
printf("double\n");
status=0;
count++;
}
// for do
else if(((ch==' ')||(ch=='\n'))&&(status==26))
{
printf("do\n");
status=0;
count++;
}
// for else
else if((ch=='e')&&(status==0))
{
status=30;
}
else if((ch=='l')&&(status==30))
{
status=31;
}
else if((ch=='s')&&(status==31))
{
status=32;
}
else if((ch=='e')&&(status==32))
{
printf("else\n");
status=0;
count++;
}
// for enum
else if((ch=='n')&&(status==30))
{
status=33;
}
else if((ch=='u')&&(status==33))
{
status=34;
}
else if((ch=='m')&&(status==34))
{
printf("enum\n");
status=0;
count++;
}
// for extern
else if((ch=='x')&&(status==30))
{
status=35;
}
else if((ch=='t')&&(status==35))
{
status=36;
}
else if((ch=='e')&&(status==36))
{
status=37;
}
else if((ch=='r')&&(status==37))
{
status=38;
}
else if((ch=='n')&&(status==38))
{
printf("extern\n");
status=0;
count++;
}
// for float
else if((ch=='f')&&(status==0))
{
status=39;
}
else if((ch=='l')&&(status==39))
{
status=40;
}
else if((ch=='o')&&(status==40))
{
status=41;
}
else if((ch=='a')&&(status==41))
{
status=42;
}
else if((ch=='t')&&(status==42))
{
printf("float\n");
status=0;
count++;
}
// for keyword for
else if((ch=='o')&&(status==39))
{
status=43;
}
else if((ch=='r')&&(status==43))
{
printf("for\n");
status=0;
count++;
}
// for goto
else if((ch=='g')&&(status==0))
{
status=44;
}
else if((ch=='o')&&(status==44))
{
status=45;
}
else if((ch=='t')&&(status==45))
{
status=46;
}
else if((ch=='o')&&(status==46))
{
printf("goto\n");
status=0;
count++;
}
// for if
else if((ch=='i')&&(status==0))
{
status=47;
}
else if((ch=='f')&&(status==47))
{
printf("if\n");
status=0;
count++;
}
//for int
else if((ch=='n')&&(status==47))
{
status=48;
}
else if((ch=='t')&&(status==48))
{
printf("int\n");
status=0;
count++;
}
// for long
else if((ch=='l')&&(status==0))
{
status=49;
}
else if((ch=='o')&&(status==49))
{
status=50;
}
else if((ch=='n')&&(status==50))
{
status=51;
}
else if((ch=='g')&&(status==51))
{
printf("long\n");
status=0;
count++;
}
// for register
else if((ch=='r')&&(status==0))
{
status=52;
}
else if((ch=='e')&&(status==52))
{
status=53;
}
else if((ch=='g')&&(status==53))
{
status=54;
}
else if((ch=='i')&&(status==54))
{
status=55;
}
else if((ch=='s')&&(status==55))
{
status=56;
}
else if((ch=='t')&&(status==56))
{
status=57;
}
else if((ch=='e')&&(status==57))
{
status=58;
}
else if((ch=='r')&&(status==58))
{
printf("register\n");
status=0;
count++;
}
//for return
else if((ch=='t')&&(status==53))
{
status=59;
}
else if((ch=='u')&&(status==59))
{
status=60;
}
else if((ch=='r')&&(status==60))
{
status=61;
}
else if((ch=='n')&&(status==61))
{
printf("return\n");
status=0;
count++;
}
// for short
else if((ch=='s')&&(status==0))
{
status=62;
}
else if((ch=='h')&&(status==62))
{
status=63;
}
else if((ch=='o')&&(status==63))
{
status=64;
}
else if((ch=='r')&&(status==64))
{
status=65;
}
else if((ch=='t')&&(status==65))
{
printf("short\n");
status=0;
count++;
}
// for sizeof
else if((ch=='i')&&(status==62))
{
status=66;
}
else if((ch=='z')&&(status==66))
{
status=67;
}
else if((ch=='e')&&(status==67))
{
status=68;
}
else if((ch=='o')&&(status==68))
{
status=69;
}
else if((ch=='f')&&(status==69))
{
printf("sizeof\n");
status=0;
count++;
}
// for signed
else if((ch=='g')&&(status==66))
{
status=70;
}
else if((ch=='n')&&(status==70))
{
status=71;
}
else if((ch=='e')&&(status==71))
{
status=72;
}
else if((ch=='d')&&(status==72))
{
printf("signed\n");
status=0;
count++;
}
//for static
else if((ch=='t')&&(status==62))
{
status=72;
}
else if((ch=='a')&&(status==72))
{
status=73;
}
else if((ch=='t')&&(status==73))
{
status=74;
}
else if((ch=='i')&&(status==74))
{
status=75;
}
else if((ch=='c')&&(status==75))
{
printf("static\n");
status=0;
count++;
}
// for struct
else if((ch=='r')&&(status==72))
{
status=76;
}
else if((ch=='u')&&(status==76))
{
status=77;
}
else if((ch=='c')&&(status==77))
{
status=78;
}
else if((ch=='t')&&(status==78))
{
printf("struct\n");
status=0;
count++;
}
// for switch
else if((ch=='w')&&(status==62))
{
status=79;
}
else if((ch=='i')&&(status==79))
{
status=80;
}
else if((ch=='t')&&(status==80))
{
status=81;
}
else if((ch=='c')&&(status==81))
{
status=82;
}
else if((ch=='h')&&(status==82))
{
printf("switch\n");
status=0;
count++;
}
// for typedef
else if((ch=='t')&&(status==0))
{
status=83;
}
else if((ch=='y')&&(status==83))
{
status=84;
}
else if((ch=='p')&&(status==84))
{
status=85;
}
else if((ch=='e')&&(status==85))
{
status=86;
}
else if((ch=='d')&&(status==86))
{
status=87;
}
else if((ch=='e')&&(status==87))
{
status=88;
}
else if((ch=='f')&&(status==88))
{
printf("typedef\n");
status=0;
count++;
}
// for union
else if((ch=='u')&&(status==0))
{
status=89;
}
else if((ch=='n')&&(status==89))
{
status=90;
}
else if((ch=='i')&&(status==90))
{
status=91;
}
else if((ch=='o')&&(status==91))
{
status=92;
}
else if((ch=='n')&&(status==92))
{
printf("union\n");
status=0;
count++;
}
// for unsigned
else if((ch=='s')&&(status==90))
{
status=93;
}
else if((ch=='i')&&(status==93))
{
status=94;
}
else if((ch=='g')&&(status==94))
{
status=95;
}
else if((ch=='n')&&(status==95))
{
status=96;
}
else if((ch=='e')&&(status==96))
{
status=97;
}
else if((ch=='d')&&(status==97))
{
printf("unsigned\n");
status=0;
count++;
}
// for void
else if((ch=='v')&&(status==0))
{
status=98;
}
else if((ch=='o')&&(status==98))
{
status=99;
}
else if((ch=='i')&&(status==99))
{
status=100;
}
else if((ch=='d')&&(status==100))
{
printf("void\n");
status=0;
count++;
}
// for void
else if((ch=='l')&&(status==99))
{
status=101;
}
else if((ch=='a')&&(status==101))
{
status=102;
}
else if((ch=='t')&&(status==102))
{
status=103;
}
else if((ch=='i')&&(status==103))
{
status=104;
}
else if((ch=='l')&&(status==104))
{
status=105;
}
else if((ch=='e')&&(status==105))
{
printf("volatile\n");
status=0;
count++;
}
// for while
else if((ch=='w')&&(status==0))
{
status=106;
}
else if((ch=='h')&&(status==106))
{
status=107;
}
else if((ch=='i')&&(status==107))
{
status=108;
}
else if((ch=='l')&&(status==108))
{
status=109;
}
else if((ch=='e')&&(status==109))
{
printf("while\n");
status=0;
count++;
}
else
{
status=0;
}
i++;
}
}
fclose(fp);
printf("Total Number of Keywords Are Found = %d",count);
return 0;
}
As you can see in the above program, there are many if-else statements. There are 32 keywords in c programming. So, whenever we read a single character from a file, then we change the value of the variable status. Because, when we read the next character then we should know the previous character and we repeat these statements until we get our keyword.
When we get our keyword, then we will print it and make the value of status variable to 0. Because it tells us that we are going to find the next character.
Here, I have written this program using Theory of Computation. From this, I have designed the DFA for this problem.
I hope you have liked this program. If you have any doubt or any feedback or you need a detail explanation for this program, then please feel free to contact me.
Thank you.
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