parse.c

/************************************************************************  
 *   parse.c  -  The parsing portion of my small shell                                     *
 *   Syntax:     myshell command1 [< infile] [| command]* [> outfile] [&]       *
 ************************************************************************/

#include <ctype.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include "parse.h"

/* parse - parse a new line 
 *
 * Accepts: nothing
 * Returns: parse information structure
 */
#define MAXLINE 81

void init_info(parseInfo *p) {
  int i;

  p->boolInfile=0;
  p->boolOutfile=0;
  p->boolBackground=0;
  p->pipeNum=0;

  for (i=0; i<PIPE_MAX_NUM; i++) {
    p->CommArray[i].command=NULL;
    p->CommArray[i].VarList[0]=NULL;
    p->CommArray[i].VarNum=0;
  }
}

void parse_command(char * command, struct commandType *comm) {
  int i=0;
  int pos=0;
  char word[MAXLINE];

  comm->VarNum=0;
  comm->command=NULL;
  comm->VarList[0]=NULL;
  while(isspace(command[i]))
    i++; 
  if (command[i] == '\0') 
    return;
  while (command[i] != '\0') {
    while (command[i] != '\0' && !isspace(command[i])) {
      word[pos++]=command[i++];
    }
    word[pos]='\0';
    comm->VarList[comm->VarNum]=malloc((strlen(word)+1)*sizeof(char));
    strcpy(comm->VarList[comm->VarNum], word);
    comm->VarNum++;
    word[0]='\0';
    pos=0;
    while(isspace(command[i]))
      i++; 
  }
  comm->command=malloc((strlen(comm->VarList[0])+1)*sizeof(char));
  strcpy(comm->command, comm->VarList[0]);
  comm->VarList[comm->VarNum]=NULL;
}

parseInfo *parse (char *cmdline) {
  parseInfo *Result;
  int i=0;
  int pos;
  int end=0;
  char command[MAXLINE];
  int com_pos;

  if (cmdline[i] == '\n' && cmdline[i] == '\0')
    return NULL;

  Result = malloc(sizeof(parseInfo));
  if (Result == NULL){
    return NULL;
  }
  init_info(Result);
  com_pos=0;
  while (cmdline[i] != '\n' && cmdline[i] != '\0') {
    if (cmdline[i] == '&') {
      Result->boolBackground=1;
      if (cmdline[i+1] != '\n' && cmdline[i+1] != '\0') {
	fprintf(stderr, "Ignore anything beyond &.\n");
      }
      break;
    }
    else if (cmdline[i] == '<') {
      Result->boolInfile=1;
      while (isspace(cmdline[++i]));
      pos=0;
      while (cmdline[i] != '\0' && !isspace(cmdline[i])) {
	if (pos==FILE_MAX_SIZE) {
	  fprintf(stderr, "Error.The input redirection file name exceeds the size limit 40\n");
	  free_info(Result);
	  return NULL;
	}
	Result->inFile[pos++] = cmdline[i++];
      }
      Result->inFile[pos]='\0';
      end =1;
      while (isspace(cmdline[i])) {
	if (cmdline[i] == '\n') 
	  break;
	i++;
      }
    }
    else if (cmdline[i] == '>') {
      Result->boolOutfile=1;
      while (isspace(cmdline[++i]));
      pos=0;
      while (cmdline[i] != '\0' && !isspace(cmdline[i])) {
	if (pos==FILE_MAX_SIZE) {
	  fprintf(stderr, "Error.The output redirection file name exceeds the size limit 40\n");
	  free_info(Result);
	  return NULL;
	}
	Result->outFile[pos++] = cmdline[i++];
      }
      Result->outFile[pos]='\0';
      end =1;
      while (isspace(cmdline[i])) {
	if (cmdline[i] == '\n') 
	  break;
	i++;
      } 
    }
    else if (cmdline[i] == '|') {
      command[com_pos]='\0';
      parse_command(command, &Result->CommArray[Result->pipeNum]);
      com_pos=0;
      end =0;
      Result->pipeNum++;
      i++;
    }
    else {
      if (end == 1) {
	 fprintf(stderr, "Error.Wrong format of input\n");
	 free_info(Result);
	 return NULL;
      }
      if (com_pos == MAXLINE-1) {
	fprintf(stderr, "Error. The command length exceeds the limit 80\n");
	free_info(Result);
	return NULL;
      }
      command[com_pos++] = cmdline[i++];
    }
  }
  command[com_pos]='\0';
  parse_command(command, &Result->CommArray[Result->pipeNum]);
  /*Result->pipeNum++;*/
  return Result;
}

void print_info (parseInfo *info) {
  int i, j;
  struct commandType *comm;

  if (NULL == info){
    printf("Null info\n");
    return;
  }
  printf("Parse struct:\n\n");
  printf("# of pipes:%d\n", info->pipeNum);
  for (i=0; i<=info->pipeNum;i++) {
    comm=&(info->CommArray[i]);
    if ((NULL == comm) || (NULL == comm->command)){
      printf("Command %d is NULL\n", i);
    } else {
      printf("Command %d is %s.\t", i+1, comm->command);
      for (j=0; j<comm->VarNum; j++) {
	printf("Arg %d: %s ", j, comm->VarList[j]);
      }
      printf("\n");
    }
  }
  printf("\n");

  if (info->boolInfile){
    printf("infile: %s\n", info->inFile);
  }else {
    printf("no input redirection.\n");
  }
  if (info->boolOutfile) {
    printf("outfile: %s\n", info->outFile);
  }else {
    printf("no output redirection.\n");
  }
  if (info->boolBackground){
    printf("Background process.\n");
  } else {
    printf("Foreground process.\n");
  }
}
 
void free_info (parseInfo *info) {
  int i,j;
  struct commandType *comm;

  if (NULL == info) return;
  for (i=0; i<PIPE_MAX_NUM;i++) {
    comm=&(info->CommArray[i]);
    for (j=0; j<comm->VarNum; j++) {
      free(comm->VarList[j]);
    }
    if (NULL != comm->command){
      free(comm->command);
    }
  }
  free(info);
}