Education Resources: 02/01/2009

DEPARTMENT OF Computer Science Compiler Design LAB PROGRAMS

1.a)Non-recursive shell script that accepts any number of argumnets and prints them in the reverse order.

Filename : 1a.sh

echo "number of arguments are : $#"

len=$#

while [ $len -ne 0 ]

eval echo \$$len

len=`expr $len - 1`

done

output :

$ chmod 777 1a.sh

$ ./1a.sh 1 2 3

number of arguments are : 3

$ ./1a.sh dilip mithun pavan

number of arguments are : 3

pavan

mithun

dilip

1.b)C program that creates a child process to read commands from the standard input and execute them ( a minimal implementation pf a shell – like a program). You can assume that no arguments will be passed to the commands to be executed.

Filename : 1b.c

#include

int main()

{

char cmd[20];

pid_t pid;

int ch;

pid=fork();

if(pid == 0)

{

printf("\n Enter the command to be executed : ");

scanf("%s",cmd);

system(cmd);

printf("\n Enter 1 to continue and 0 to exit : ");

scanf("%d",&ch);

}

while(ch!=0);

}

wait();

}

output :

$ cc 1b.c

$ ./a.out

Enter the command to be executed : date

Tue Mar 1 22:05:52 IST 2005

Enter 1 to continue and 0 to exit : 1

Enter the command to be executed : cal

March 2005

Su Mo Tu We Th Fr Sa

1 2 3 4 5

6 7 8 9 10 11 12

13 14 15 16 17 18 19

20 21 22 23 24 25 26

27 28 29 30 31

Enter 1 to continue and 0 to exit : 0

Note : The program 1b can also written as given below in an more appropriate form

Filename : 1b.c

#include

#define MAXLINE 10

int main()

{

char buf[MAXLINE];

pid_t pid;

int status;

system("tput clear");

printf("Type any command(without options):\n");

printf("#");

fgets(buf,MAXLINE,stdin);

buf[strlen(buf)-1]=0;

while(strlen(buf)!=0)

{

if((pid=fork())<0)

{

printf("fork error");

}

else if(pid==0)

{

execlp(buf,buf,(char *) 0);

printf("couldn't execute : %s\n",buf);

exit(0);

}

if((pid=waitpid(pid,&status,0))<0)

printf("waitpid error");

printf("#");

fgets(buf,MAXLINE,stdin);

buf[strlen(buf)-1]=0;

}

exit(0);

}

output :

$ cc 1b.c

$ ./a.out

# date

Tue Mar 1 22:05:52 IST 2005

2.a)Shell script that accepts two file names as arguments, checks if the permissions of these files are identical and if the permissions are identical, outputs the common permission, otherwise outputs each file name followed by its permission.

Filename : 2a.sh

ls -l $1 | cut -d " " -f 1 > file1per

ls -l $2 | cut -d " " -f 1 > file2per

if cmp file1per file2per

then

echo "Both the files have same permission"

cat file1per

else

echo "Both the files have different permission"

echo "The permission of first file $1 is "

cat file1per

echo "The permission of second file $2 is "

cat file2per

output :

$chmod 777 2a.sh

$cat > file1

this is first file content

$cat > file2

this is second file content

$./2a.sh file1 file2

Both the files have same permission

-rw-r--r--

$chmod 777 file2

$./2a.sh file1 file2

file1per file2per differ: byte 4, line 1

Both the files have different permission

The permission of first file file1 is

-rw-r--r--

The permission of second file file2 is

-rwxrwxrwx

2.b)C program to create a file with 16 bytes of arbitary data from the beginning and another 16 bytes of arbitary data from an offset of 48. Display the file contents to demonstrate how the hole in file is handled

Filename : 2b.c

#include

int main()

{

int fd;

char buf1[]="Department of IS";

char buf2[]="Department of CS";

fd=creat("ise",0622);

if(fd < 0)

{

printf("\n Error in creating file");

exit(0);

}

write(fd,buf1,16);

lseek(fd,48,SEEK_SET);

write(fd,buf2,16);

exit(0);

}

output :

$cc 2b.c

$./a.out

$od -c ise

0000000 D e p a r t m e n t o f I S

0000020 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0

0000060 D e p a r t m e n t o f C S

0000100

3.a)Shell script that takes a valid directory names as as argument and recursively descends all the subdirectories, finds the maximum length of any file in that hierarchy and writes this maximum valut to the standard output.

Filename : 3a.sh

maxsize=`ls -lR $1 | grep '^-' | cut -c 35-42 | sort -n | tail -1`

echo "The max size of the file in directort $1 is $maxsize bytes"

output :

$chmod 777 3a.sh

$ls -l

total 12

-rwxr-xr-x 1 root root 148 Mar 1 22:17 1a.sh

-rwxr-xr-x 1 root root 366 Mar 1 22:17 2a.sh

-rwxrwxrwx 1 root root 192 Mar 1 22:17 3a.sh

$./3a.sh /root/6ise/unix

The max size of the file in directort /root/6ise/unix is 366 bytes

3.b)C program that accepts valid file names as coomand line arguments and for each of the arguments, prints the type of the file ( Regular file, directory file, character special file, block special file, symbolic link etc .. )

Filename : 3b.c

#include

int main(int argc, char *argv[])

{

int i;

struct stat buf;

for(i=1; i< argc; i++)

{

printf("%s: ", argv[i]);

lstat(argv[i],&buf);

if(S_ISREG(buf.st_mode))

printf("file is a regular file\n");

if(S_ISDIR(buf.st_mode))

printf("file is a directory file\n");

if(S_ISCHR(buf.st_mode))

printf("file is a character file\n");

if(S_ISBLK(buf.st_mode))

printf("file is a block file\n");

if(S_ISLNK(buf.st_mode))

printf("file is a symbolic link file\n");

}

exit(0);

}

output :

$cc 3b.c

$./a.out /root/6ise/3b.c

/root/6ise/3b.c: file is a regular file

$./a.out /root/6ise/3b.c /root/6ise

/root/6ise/3b.c: file is a regular file

/root/6ise: file is a directory file

$./a.out /dev/tty

/dev/tty: file is a character file

4.a)Shell script that accepts pathnames and creates all the components in that path names as directories. For example, if the script name in mpe, then the command mpe a/b/c/d should create directories a,a/b,a/b/c and a/b/c/d.

Filename : 4a.sh

if [ $# -le 0 -o $# -gt 1 ]

then

echo "Improper Usage pathname required"

else

mkdir -p $1

output :

$chmod 777 4a.sh

$./4a.sh a/b/c/d

$cd a

$ls

$cd b

$ls

$cd c

$ls

4.b)C program that accepts one command-line argument,executes the arguments as a shell command,determines the time taken by it and prints the time values. Use the “times” function and the “tms” structure. The code need not include error checking.

Filename : 4b.c

#include

int main(int argc, char *argv[])

{

struct tms tms1,tms2;

clock_t start,end;

long clktck = sysconf(_SC_CLK_TCK);

start=times(&tms1);

system(argv[1]);

end=times(&tms2);

printf("\n The total execution(wall clock) time is %3.2f\n",(end- start) / (double) clktck);

printf("\n The User cpu time is %3.2f\n",(tms2.tms_utime - tms1.tms_utime) / (double) clktck);

printf("\n The System cpu time is %3.2f\n",(tms2.tms_stime - tms1.tms_stime) / (double) clktck);

printf("\n The User cpu time of the terminated child process is %3.2f\n",(tms2.tms_cutime - tms1.tms_cutime) / (double) clktck);

printf("\n The System cpu time of the terminated child process is %3.2f\n",(tms2.tms_cstime - tms1.tms_cstime) / (double) clktck);

exit(0);

}

output :

$cc 4b.c

$./a.out ls

10a.awk 1b1 2b 3b.c 5a.sh 5b.c 7b.awk 9b.pl file1per

10b 1b1.c 2b.c 4a.sh 5b 6a.sh 8a.sh a file2

10b.c 1b.c 3a.sh 4b 5b1 6b.c 8b.pl a.out file2per 2a.sh 3b 4b.c 5b1.c 7a.sh 9a.sh

The total execution(wall clock) time is 0.01

The User cpu time is 0.00

The System cpu time is 0.00

The User cpu time of the terminated child process is 0.00

The System cpu time of the terminated child process is 0.01

5.a)shell script that accepts valid log-in names as arguments and prints their corresponding home directories. If no arguments are specified, print a suitable error message.

Filename :5a.sh

if [ $# -lt 1 ]

then

echo "Improper Usage :$0 No Login Name"

for i

awk -F: '{print $1,$6}' /etc/passwd | grep -i ^"$i"

done

output :

$chmod 777 5a.sh

$./5a.sh

Improper Usage :./5a.sh No Login Name

$./5a.sh girish

girish /home/girish

$./5a.sh root

root /root

5.b)C program that accepts a valid directory names as a command line argument and lists all the files in the given directory as well as all the subsequent suddirectories.

Filename : 5b.c

#include

int main(int argc, char *argv[])

{

int i;

char str[50];

for(i=1;i

{

strcpy(str," ls -R ");

strcat(str,argv[i]);

system(str);

}

output :

$cc 5b1.c

$./a.out /root/6ise

/root/6ise:

10a.awk 1b1 2b 3b.c 5a.sh 5b.c 7b.awk 9b.pl file1per

10b 1b1.c 2b.c 4a.sh 5b 6a.sh 8a.sh a file2

10b.c 1b.c 3a.sh 4b 5b1 6b.c 8b.pl a.out file2per

1a.sh 2a.sh 3b 4b.c 5b1.c 7a.sh 9a.sh file1 in10

/root/6ise/a:

/root/6ise/a/b:

/root/6ise/a/b/c:

/root/6ise/a/b/c/d:

/root/6ise/unix:

1a.sh 2a.sh 3a.sh

6.a)shell script to implement terminal locking. It should prompt the user for a password. After accepting the password entered by the user,it must prompt again for password confirmation (to retype the passwprd). If a match occurs,it must lock the terminal and prompt for the password. If the proper password is entered, the terminal must be unlocked. Note the script must be written to disregard BREAK,control-D etc. No time limit need be implemented for the lock duration.

Filename :6a.sh

trap "" 1 2 3

stty -echo

echo "Enter your password:"

read key1

echo "Retype your password:"

read key2

if [ $key1 = $key2 ]

then

clear

key3=""

until [ "$key3" = "$key2" ]

read key3

done

else

echo "Wrong password . you are a illegal user"

stty echo

output :

$./6a.sh

Enter your password :

Retype your password :

NOTE : Now the terminal gets locked and to invoke the terminal you have to re-type the password.

6.b)C program to prompt the user for the name of an environment variable and print its value if it is defined and a suitable message otherwise; and to repeat the process if user wants it.

Filename : 6b.c

#include

int main(void)

{

char name[25];

int i=1;

char *p;

{

printf("\n Enter any Environment variable :");

scanf("%s",name);

p=getenv(name);

if(p)

printf("%s",p);

else

printf("\n Environment variable donot match");

printf("\n Want to continue 1--yes 0-no :\n");

scanf("%d",&i);

}

while(i!=0);

}

output :

$cc 6b.c

$./a.out

Enter any Environment variable :HOME

/root

Want to continue 1--yes 0-no :

Enter any Environment variable :PATH

/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin

Want to continue 1--yes 0-no :

7.a)Shell script that accepts file names specified as arguments and creates a shell script that contains this file as well as the code to recreate these files. Thus if the script generated by your script is executed,it would recreate the original files.

Filename : 7a.sh

echo '#to bundle,sh this file'

for i in $*

echo "echo $i 1>&2"

echo "cat >$i <<'End of $i'"

cat $i

echo "End of $i"

done

output:

$chmod 777 7a.sh

$ls

10b.c 1b.c 4a.sh 5a.sh 5b.c 6a.sh 6b.c 7a.sh 8a.sh 9a.sh a

$cat > file1

this is first file

$cat > file2

this is second file

$ls

10b.c 4a.sh 5b.c 6b.c 8a.sh a file2

1b.c 5a.sh 6a.sh 7a.sh 9a.sh file1

$./7a.sh file1 file2 > new.sh

$ls

10b.c 4a.sh 5b.c 6b.c 8a.sh a file2

1b.c 5a.sh 6a.sh 7a.sh 9a.sh file1 new.sh

$rm file1

rm: remove regular file `file1'? y

$rm file2

rm: remove regular file `file2'? y

$ls

10b.c 1b.c 4a.sh 5a.sh 5b.c 6a.sh 6b.c 7a.sh 8a.sh 9a.sh a new.sh

$chmod 777 new.sh

$./new.sh

file1

file2

$ls

10b.c 4a.sh 5b.c 6b.c 8a.sh a file2

1b.c 5a.sh 6a.sh 7a.sh 9a.sh file1 new.sh

$cat file1

this is first file

$cat file2

this is second file

7.b)Awk script to delete duplicated lines from a text file. The order of the original must remain unchanged.

Filename : 7b.awk

{

found=0

for(i=0;i

if(lines[i] == $0)

{

found=1

break

}

if(!found)

{

lines[nlines++]=$0

print $0

}

ouput :

$cat > input

ise

vit

cse

bangalore

$awk -f 7b.awk input

ise

vit

cse

bangalore

$cat input

ise

vit

cse

bangalore

8.a)Shell script to find and display all the links of a file specified as the first argument to the script. The second argument is optional,can be used to specify the directory in which the search is to begin. If this second argument is not present, the search is to begin in current working directory. In either case, the starting directory as well as its subdirectories al all levels must be searched. The script need not include any error checking.

Filename : 8a.sh

file="$1"

if [ $# -eq 1 ]

then

directory="."

else

directory="$2"

set -- $( ls -l "$file" )

linkcnt=$2

if [ "$linkcnt" = 1 ]

then

echo "no other links to $file" 1>&2

exit 0

set -- $( ls -i "$file" )

inode=$1

find "$directory" -xdev -inum $inode -print

output :

$chmod 777 8a.sh

$cat > input

this is a simple text file.

$./8a.sh input

no other links to input

$ln input ouput

$./8a.sh input

./input

./ouput

8.b)PERL script that echoes its command line arguments,one per line after translating all lower case letters to upper case.

Filename : 8b.pl

foreach $string (@ARGV)

{

$string=~tr/a-z/A-Z/;

print("$string\n");

}

ouput :

$perl 8b.pl welcome to unix lab

WELCOME

UNIX

LAB

9.a)Shell script to display the calendar for current month with current date replaced by * and ** depending on whether date has one digit or two digit.

Filename : 9a.sh

cal >daymo

set `date`

y=`expr $3 : '.*'`

if [ $y -eq 1 ]

then

sed "s/ $3/ \*/" daymo

else

sed "s/ $3/ \**/" daymo

rm daymo

output :

$chmod 777 9a.sh

$./9a.sh

March 2005

Su Mo Tu We Th Fr Sa

1 2 3 4 5

6 7 8 9 10 11 12

13 14 15 16 17 ** 19

20 21 22 23 24 25 26

27 28 29 30 31

9.b)PERL program to convert an unsigned binary number(supplied as arg) to decimal(for example if the arg is 10110 the output should be 22). If an argument is present,it can be a valid binary number and if no argument is present, the program should display an error message.

Filename : 9b.pl

if(@ARGV==0)

{

print("INVALID argument\n");

}

else

{

$num=0;

$mul=1;

while($ARGV[0] != " ")

{

$num = $num + chop($ARGV[0]) * $mul;

$mul = $mul * 2;

}

print("$num\n");

}

output :

$perl 9b.pl 101

$perl 9b.pl 1010

10.a)Awk script that folds long line into 40 columns. Thus any line that exceeds 40 characters must be broken after 40th and is to be continued with the residue. The inputs to be supplied through a text file created by the user.

Filename : 10a.awk

{

x=$0

while(length(x) > 40)

{

printf("%sX\n",substr(x,1,40))

x=substr(x,41,length(x)-40)

}

printf("%s\n",x)

}

ouput :

$cat > xyz.txt

this is a text file that is supplied as an input to the 10th program

unix is really a nice and interesting subject

$awk -f 10a.awk xyz.txt

this is a text file that is supplied as

an input to the 10th program

unix is really a nice and interesting su

bject

10.b)C program to do the following. Using fork( ) create a child process. The child process prints its own process-id and id of its parent and then exits.The parent process waits for its child to finish(by executing wait( )) and prints its own process-id and the id of its child process and then exits.

Filename : 10b.c

#include

int main()

{

pid_t pid;

if((pid=fork())<0)

printf("fork error");

if(pid==0)

{

printf("\n This is child process ");

printf("\n Child PID :%d",getpid());

printf("\n Parent PID :%d\n",getppid());

exit(0);

}

else

{

wait();

printf("\n This is parent process");

printf("\n Parent PID :%d",getpid());

printf("\n Child PID :%d",pid);

exit(0);

}

output :

$cc 10b.c

$./a.out

This is child process

Child PID :3122

Parent PID :3121

This is parent process

Parent PID :3121

Child PID :3122

1.a)program to count the number of characters, words, spaces and lines in a given input file

Filename : 1a.l

int ch=0,bl=0,li=0,wr=0;

[\n] {li++;wr++;}

[\t] {bl++;wr++;}

[" "] {bl++;wr++;}

[^\n\t] {ch++;}

int main()

{

FILE *fp;

char file[10];

printf("enter the file name :");

scanf("%s",file);

fp=fopen(file,"r");

yyin=fp;

yylex();

printf("character=%d\nblank=%d\nline=%d\nword=%d\n",ch,bl,li,wr);

return 0;

}

output :

$cat > input

girish rao salanke

$lex 1a.l

$cc lex.yy.c -ll

$./a.out

enter the file name :input

character=16

blank=2

line=1

word=3

1.b)Program to count the number of comment lines in a given C program. Also eliminate them and copy that program into a separate file.

Filename : 1b.l

int com=0;

"/*"[^\n]+"*/" {com++;fprintf(yyout," ");}

int main()

{

printf("write a c program\n");

yyout=fopen("output","w");

yylex();

printf("comment=%d\n",com);

return 0;

}

output :

$lex 1b.l

$cc lex.yy.c -ll

$./a.out

write a c program

#include

int main()

{

int a,b;

/* float c; */

printf("hai");

/* printf("hello");

}

(NOTE : press Control-d)

comment=1

$cat output

#include

int main()

{

int a,b;

printf("hai");

printf("hello");

}

2.a)Program to recognize a valid arithmetic expression and identify the identifiers and operators present. Print them separately.

Filename : 2a.l

#include

int a=0,s=0,m=0,d=0,ob=0,cb=0;

int flaga=0,flags=0,flagm=0,flagd=0;

id [a-zA-Z]+

{id} {printf("\n %s an identifier\n",yytext);}

[+] {a++;flaga=1;}

[-] {s++;flags=1;}

[*] {m++;flagm=1;}

[/] {d++;flagd=1;}

[(] {ob++;}

[)] {cb++;}

int main()

{

printf("enter the exp\n");

yylex();

if(ob-cb==0)

{

printf("valid exp\n");

}

else

{

printf("invalid exp\n");

}

printf("add=%d\nsub=%d\nmul=%d\ndiv=%d\n",a,s,m,d);

printf("operators are:\n");

if(flaga)

{

printf("+\n");

}

if(flags)

{

printf("-\n");

}

if(flagm)

{

printf("*\n");

}

if(flagd)

{

printf("/\n");

}

return 0;

}

output :

$lex 2a.l

$cc lex.yy.c -ll

$./a.out

enter the exp

(a+b*c)

a an identifier

b an identifier

c an identifier

(NOTE : press Control-d)

valid exp

add=1

sub=0

mul=1

div=0

operators are:

$./a.out

enter the exp

(a+

a an identifier

invalid exp

add=1

sub=0

mul=0

div=0

operators are:

2.b)Program to recognize whether a given sentence is simple or compound

Filename : 2b.l

/*only 'AND','OR','BUT' are implemented , if needed we can for other possibilities*/

int flag=0;

(""[aA][nN][dD]"")|(""[oO][rR]"")|(""[bB][uU][tT]"") { flag=1;}

int main()

{

printf("enter the sentence\n");

yylex();

if(flag==1)

{

printf("compound sentence\n");

}

else

{

printf("simple sentence\n");

}

return 0;

}

output :

$lex 2b.l

$cc lex.yy.c -ll

$./a.out

enter the sentence

1 am an indian

(NOTE : press Control-d)

simple sentence

$./a.out

enter the sentence

cse or ise

cse ise

(NOTE : press Control-d)

compound sentence

3) Program to recognize and count the number of identifiers in a given input file.

Filename : 3.l

#include

int count=0;

op [+-*/]

letter [a-zA-Z]

digit [0-9]

id {letter}*|({letter}{digit})+

notid ({digit}{letter})+

[\t\n]+

("int") |

("float") |

("char") |

("case") |

("default") |

("if") |

("for") |

("printf") |

("scanf") {printf("%s is a keyword\n",yytext);}

{id} {printf("%s is an identifier\n",yytext);count++;}

{notid} {printf("%s is not an identifier\n",yytext);}

int main()

{

FILE *fp;

char file[10];

printf("\n Enter the file name : ");

scanf("%s",file);

fp=fopen(file,"r");

yyin=fp;

yylex();

printf("total identifiers are:%d\n",count);

return 0;

}

output :

$cat input6

int

float

78f

90gh

are

case

default

printf

scanf

$lex 3.l

$cc lex.yy.c -ll

$./a.out

Enter the file name : input6

int is a keyword

float is a keyword

78f is not an identifier

90g is not an identifier

h is an identifier

a is an identifier

d is an identifier

are is an identifier

case is a keyword

default is a keyword

printf is a keyword

scanf is a keyword

total identifiers are:4

4.a) Program to recognize a valid arithmetic expression that uses operators +, - , * and /.

Filename : 4a.l

#include "y.tab.h"

id [a-zA-Z]+

num [0-9]+

{id} {return id;}

{num} {return num;}

([+])|([-])|([*])|([/])|([(])|([)]) {return yytext[0];}

[\n] {return '\n';}

. {return 0;}

Filename : 4a.y

#include

%token id num

%left '+' '-'

%left '*' '/'

stat:|exp '\n' {printf("valid\n");exit(0);}

exp:exp '+' exp

|exp '-' exp

|exp '*' exp

|exp '/' exp

|'(' exp ')'

|id

|num

;

main()

{

printf("enter the exp\n");

yyparse();

}

int yyerror()

{

printf("invalid\n");

exit(0);

}

output :

$lex 4a.l

$yacc -d 4a.y

$cc lex.yy.c y.tab.c -ll

$./a.out

enter the exp

(a+b*c)

valid

$./a.out

enter the exp

(a+

invalid

4.b) Program to recognize a valid varaiable, which starts with aletter, followed by any number of letters or digits.

Filename : 4b.l

#include "y.tab.h"

[0-9]+ {return digit;}

[a-zA-Z]+ {return letter;}

[\n] {return yytext[0];}

Filename : 4b.y

#include

%token digit letter

id:exp '\n' {printf("valid variable\n");exit(0);}

exp:letter

|exp digit

|exp letter

|error {yyerror("invalid\n");exit(0);}

;

main()

{

printf("enter the variable\n");

yyparse();

}

yyerror(char *s)

{

printf("%s\n",s);

}

output :

$lex 4b.l

$yacc -d 4b.y

$cc lex.yy.c y.tab.c -ll

$./a.out

enter the variable

aab4

valid variable

$./a.out

enter the variable

6ab

syntax error

invalid

5.a) Program to evaluate an arithmetic expression invloving operators +, -, * , and /.

Filename : 5a.l

#include "y.tab.h"

#include

extern yylval;

[0-9]+ {yylval=atoi(yytext); return num;}

[+] return '+';

[-] return '-';

[*] return '*';

[/] return '/';

[/t]+ ;

[\n] return 0;

. {return yytext[0];}

Filename : 5a.y

#include

%token num

%left '-' '+'

%left '*' '/'

start:exp {printf("%d\n",$$);}

exp:exp '+' exp {$$=$1+$3;}

|exp '-' exp {$$=$1-$3;}

|exp '*' exp {$$=$1*$3;}

|exp '/' exp

{ if($3==0)

yyerror("error");

else

$$=$1/$3;

}

|'('exp')' {$$=$2;}

|num {$$=$1;}

;

main()

{

printf("enter the exp in terms of integers\n");

if(yyparse()==0)

printf("success\n");

}

yyerror()

{

printf("error\n");

}

output :

$lex 5a.l

$yacc -d 5a.y

$cc lex.yy.c y.tab.c -ll

$./a.out

enter the exp in terms of integers

7*2

success

$./a.out

enter the exp in terms of integers

9-2

success

$./a.out

enter the exp in terms of integers

8/2

success

5.b) Program to recognize strings ‘aaab’ , ’abbb’ , ’ab’ , ’a’ using the grammar (aⁿbⁿ, n>=0)

Filename : 5b.l

#include "y.tab.h"

[a] return A;

[b] return B;

Filename : 5b.y

#include

%token A B

S:A S B

;

main()

{

printf("enter the string\n");

if(yyparse()==0)

{

printf("valid\n");

}

yyerror(char *s)

{

printf("%s\n",s);

}

output :

$lex 5b.l

$yacc -d 5b.y

$cc lex.yy.c y.tab.c -ll

$./a.out

enter the string

aabb

(NOTE : press Control-d)

valid

$./a.out

enter the string

aab

syntax error

6) Program to recognize the grammar (aⁿb, n>=10)

Filename : 6.l

#include "y.tab.h"

[a] return A;

[b] return B;

Filenmae : 6.y

#include

%token A B

stat:exp B

;

exp:A A A A A A A A A exp1

;

exp1:A exp2

|A A exp2

|A A A exp2

|A A A A exp2

;

exp2:A

;

main()

{

printf("enter the string\n");

if(yyparse()==0)

{

printf("valid\n");

}

yyerror(char *s)

{

printf("error\n");

}

output :

$lex 6.l

$yacc -d 6.y

$cc lex.yy.c y.tab.c -ll

$./a.out

enter the string

aaaaaaaaaaaab

valid

$./a.out

enter the string

aab

error

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