8/7/2019 Instructions for using vi

1/3

Instructions for using vi

1. Open a terminal window2. Typevi prg1a.l3. The vieditorisnow openin commandmode4. Press thei key5. Now editorisininsert mode6. Start typing theprogram7. To save theprogramswitch back to commandmod(Press esckey for this)8. Them type :wq9. Programissaved and youshould be back to the terminal window

To run a lex program

1. Type lexprg1a.l2. This will generate lex.yy.c3. Thendogcc lex.yy.c4. Now you have the a.out file5. Now run thisusing ./a.out test1.txt

Introduction to VI:The command tostart the VI editorisvi, followed by the filename. Forexample to

edit a file calledtemporary, you would typevi temporary and thenreturn.

The VI editor hastwomodes andinorder toget out of VI, you have to beincommandmode. Hit thekey

labeled "Escape" or "Esc" (If your terminal doesnot havesuch a key, then try ^[,or control-[.) toget into

commandmode. If you were already in the commandmode when you hit "Escape",don't worry. It

might beep, but you will still bein thecommandmode.

The command to quit out of VI is :q. Onceincommandmode, type colon, and'q', followed by return.

The command tosave the contentsof theeditoris :w. You can combine the above command with the

quit command,or :wq.

The first thingmost users learn about the VI editoris that it has twomodes: commandandinsert. The

commandmode allows theentry of commands tomanipulate text. Theinsertmodeputs anything typed

on thekeyboardinto the current file.

VI startsout incommandmode. There areseveral commands that put the VI editorintoinsertmode.

Themost commonly used commands toget intoinsert mode are a andi.

a enterinsertmode, the characters typedin will beinserted after the current cursorposition. If you

specify a count, all the text that had beeninserted will berepeated that many times.

i enterinsertmode, the characters typedin will beinserted before the current cursorposition. If you

specify a count, all the text that had beeninserted will berepeated that many times.

8/7/2019 Instructions for using vi

2/3

Prg 1b

%optionnoyywrap

%{

#include

int c=0;

%}

%%

("/*"[ a-zA-Z0-9''\n\t.]*"*/") c++;

("//"[\n]?[ a-zA-Z0-9]*) c++;

[a-zA-Z0-9(){}.\,#]* {fprintf(yyout,"%s",yytext);}

%%

main(int argc,char *argv[])

{

if(argc!=3)

{

printf("\nusage:");

return(0);

}

yyin=fopen(argv[1],"r");

yyout=fopen(argv[2],"w");

yylex();

printf("\nnoof comment linesis %d",c);

}

Prg 1a

%optionnoyywrap

%{

unsigned wordCount=0,charCount=0,lineCount=0,spaceCount=0;%}

word [^ \t\n]+

line [\n]

space [" "]

tab [\t]

%%

{word} {wordCount++;

charCount+=yyleng;}

{line} {lineCount=lineCount+1;}

{space} {spaceCount=spaceCount+1;}

{tab} {spaceCount=spaceCount+5;}

%%

main(argc,argv)

int argc;

char **argv;

{if(argc>1){

FILE *file;

file=fopen(argv[1],"r");

8/7/2019 Instructions for using vi

3/3