a#include "smallsh.h" /*include file for example*/
/*program buffers and work pointers*/
static char inpbuf[MAXBUF], tokbuf[2*MAXBUF],
*ptr = inpbuf, *tok = tokbuf;
userin(p) /*print prompt and read a line*/
char *p;
{
int c, count;
/*initialization for later routines*/
ptr = inpbuf;
tok = tokbuf;
/*display prompt*/
printf("%s ",p);
for(count = 0;;)
{
if((c = getchar()) == EOF)
return(EOF);
if(count<MAXBUF)
inpbuf[count++] = c;
if(c == '\n' && count <MAXBUF)
{
inpbuf[count] = '\0';
return(count);
}
/*if line too long restart*/
if(c == '\n')
{
printf("smallsh:input line too long\n");
count = 0;
printf("%s",p);
}
}
}
gettok(outptr) /*get token and place into tokbuf*/
char **outptr;
{
int type;
*outptr = tok;
/*strip white space*/
for(;*ptr == ' ' || *ptr == '\t'; ptr++)
;
*tok++ = *ptr;
switch(*ptr++)
{
case '\n':
type = EOL; break;
case '&':
type = AMPERSAND; break;
case ';':
type = SEMICOLON; break;
case '#':
type = POUND; break;
default:
type = ARG;
while(inarg(*ptr))
*tok++ = *ptr++;
}
*tok++ = '\0';
return(type);
}
static char special[]=
{' ', '\t', '&', ':', '\n', '\0'};
inarg(c) /*are we in an ordinary argument*/
char c;
{
char *wrk;
for(wrk = special;*wrk != '\0';wrk++)
if(c == *wrk)
return(0);
return(1);
}
#include "smallsh.h"
procline() /*process input line*/
{
char *arg[MAXARG+1]; /*pointer array for runcommand*/
int toktype; /*type of token in command*/
int narg; /*number of arguments so far*/
int type; /*FOREGROUND or BACKGROUND*/
for(narg = 0;;)
{
/*loop FOREVER*/
/*take action according to token type*/
switch(toktype = gettok(&arg[narg]))
{
case ARG:
if(narg<MAXARG)
narg++;
break;
case EOL:
case SEMICOLON:
case AMPERSAND:
case POUND:
type = (toktype == AMPERSAND) ?
BACKGROUND : FOREGROUND;
if(narg!=0)
{
arg[narg] = NULL;
runcommand(arg, type);
}
if((toktype == EOL)||(toktype=POUND))
return;
narg = 0;
break;
}
}
}
#include "smallsh.h"
/*execute a command with optional wait*/
runcommand(cline,where)
char **cline;
int where;
{
int pid, exitstat, ret;
if((pid = fork()) <0)
{
perror("smallsh");
return(-1);
}
if(pid == 0)
{
/*child*/
execvp(*cline, cline);
perror(*cline);
exit(127);
}
/*code for parent*/
/*if background process print pid and exit*/
if(where == BACKGROUND)
{
printf("[Process id %d]\n", pid);
return(0);
}
/*wait until process pid exists*/
while( (ret=wait(&exitstat)) != pid && ret != -1)
;
return(ret == -1 ? -1 : exitstat);
}
#include "smallsh.h"
char *prompt = "Command>"; /*prompt*/
main()
{
while(userin(prompt) != EOF)
procline();
}
