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parser.c
229 lines (183 loc) · 4.28 KB
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parser.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "parser.h"
#include "shell.h"
/* Determine if a token is a special operator (like '|') */
int is_operator(char *token) {
/**
* Optional: edit this if you wish to parse other operators
* like ";", "&&", etc.
*/
return (strcmp(token, "|") == 0);
}
/* Determine if a command is builtin */
int is_builtin(char *token) {
/**
* Optional: Edit this if you wish to handle more builtin commands
*/
return (strcmp(token, "cd") == 0 || strcmp(token, "exit") == 0);
}
/* Determine if a path is relative or absolute (relative to root) */
int is_relative(char* path) {
return (path[0] != '/');
}
/* Determine if a command is complex (has an operator like pipe '|') */
int is_complex_command(char **tokens) {
int i = 0;
while(tokens[i]) {
if (is_operator(tokens[i]))
return 1;
i++;
}
return 0;
}
/* Parse a line into its tokens/words */
void parse_line(char *line, char **tokens) {
while (*line != '\0') {
/* Replace all whitespaces with \0 */
while (*line == ' ' || *line == '\t' || *line == '\n')
*line++ = '\0';
/* Store the position of the token in the line */
*tokens++ = line;
//printf("token: %s\n", *(tokens-1));
/* Ignore non-whitespaces, until next whitespace delimiter */
while (*line != '\0' && *line != ' ' &&
*line != '\t' && *line != '\n')
line++;
}
*tokens = '\0';
}
int extract_redirections(char** tokens, simple_command* cmd) {
int i = 0;
int skipcnt = 0;
while(tokens[i]) {
int skip = 0;
if (!strcmp(tokens[i], ">")) {
if(!tokens[i+1])
return -1;
cmd->out = tokens[i+1];
skipcnt += 2;
skip = 1;
}
if (!strcmp(tokens[i], "<")) {
if(!tokens[i+1])
return -1;
cmd->in = tokens[i+1];
skipcnt += 2;
skip = 1;
}
if (!strcmp(tokens[i], "2>")) {
if(!tokens[i+1])
return -1;
cmd->err = tokens[i+1];
skipcnt += 2;
skip = 1;
}
if (!strcmp(tokens[i], "&>")) {
if(!tokens[i+1])
return -1;
cmd->out = tokens[i+1];
cmd->err = tokens[i+1];
skipcnt += 2;
skip = 1;
}
if(skip) i++;
i++;
}
if(skipcnt == 0) {
cmd->tokens = tokens;
return 0;
}
cmd->tokens = malloc((i-skipcnt+1) * sizeof(char*));
int j = 0;
i = 0;
while(tokens[i]) {
if (!strcmp(tokens[i], "<") ||
!strcmp(tokens[i], ">") ||
!strcmp(tokens[i], "2>") ||
!strcmp(tokens[i], "&>"))
i += 2;
else
cmd->tokens[j++] = tokens[i++];
}
cmd->tokens[j] = 0;
return 0;
}
/* Construct command */
command* construct_command(char** tokens) {
/* Initialize a new command */
command *cmd = malloc(sizeof(command));
cmd->cmd1 = cmd->cmd2 = NULL;
cmd->scmd = NULL;
if (!is_complex_command(tokens)) {
/* Simple command */
cmd->scmd = malloc(sizeof(simple_command));
if (is_builtin(tokens[0])) {
cmd->scmd->builtin = 1;
cmd->scmd->tokens = tokens;
}
else {
cmd->scmd->builtin = 0;
int err = extract_redirections(tokens, cmd->scmd);
if (err == -1) {
printf("Error extracting redirections!\n");
return NULL;
}
}
}
else {
/* Complex command */
char **t1 = tokens, **t2;
int i = 0;
while(tokens[i]) {
if(is_operator(tokens[i])) {
strncpy(cmd->oper, tokens[i], 2);
tokens[i] = 0;
t2 = &(tokens[i+1]);
break;
}
i++;
}
/* Recursively construct the rest of the commands */
cmd->cmd1 = construct_command(t1);
cmd->cmd2 = construct_command(t2);
}
return cmd;
}
/* Release resources */
void release_command(command *cmd) {
if(cmd->scmd)
if(cmd->scmd->in || cmd->scmd->out || cmd->scmd->err)
free(cmd->scmd->tokens);
if(cmd->cmd1)
release_command(cmd->cmd1);
if(cmd->cmd2)
release_command(cmd->cmd2);
}
/* Print command */
void print_command(command *cmd, int level) {
int i;
for(i = 0; i < level; i++)
printf(" ");
if(cmd->scmd) {
i = 0;
while(cmd->scmd->tokens[i]) {
printf("%s ", cmd->scmd->tokens[i]);
i++;
}
if(cmd->scmd->in)
printf("< %s ", cmd->scmd->in);
if(cmd->scmd->out)
printf("> %s ", cmd->scmd->out);
if(cmd->scmd->err)
printf("2> %s ", cmd->scmd->err);
printf("\n");
return;
}
printf("Pipeline:\n");
if(cmd->cmd1)
print_command(cmd->cmd1, level+1);
if(cmd->cmd2)
print_command(cmd->cmd2, level+1);
}