我对cd和历史的结果:
sgraham @ myshell:/ home / class / sgraham / proj1> cd ..(工作正常)
sgraham @ myshell:/ home / class / sgraham> cd ..(不工作)
sgraham @ myshell:/ home / class / sgraham> cd ..(不工作) cd:参数太多
sgraham @ myshell:/ home / class / sgraham> history
sgraham @ myshell:/家庭/类/ sgraham> (不打印历史记录)
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#define MAX_COMMAND_SIZE 80
#define MAX_ARGS 9
#define HIS_SIZE 100
typedef struct
{
int argument; // userCom arguments
char *arg[MAX_ARGS + 1]; // userCom arguments array
char *history[HIS_SIZE]; //history array
char *input; // hold input file
char *output; // hold output file
} Command;
int main()
{
Command userCom = {0}; //holds userCom struct
const char *whitespace = " \n\r\t\v\f"; // userCom delimiting chars
char* username = getenv("USER"); //Get user name
char* curDirect = getenv("HOME"); //get cwd
char* token[MAX_ARGS];
char* cwd;
char* buf;
char* cmd;
char buffer[MAX_COMMAND_SIZE + 1]; //hold userCom line
//char history[HIS_SIZE][MAX_ARGS +1]; //2D array for history
int tok = 0;
int new;
int i;
int limit;
int last = 0;
int hist = 0; //initialize history size to 0
long size;
struct stat buff; //holds file information
//gets current working directory and also changes buffer if necessary
size = pathconf(".", _PC_PATH_MAX);
if ((buf = (char *)malloc((size_t)size)) != NULL)
cwd = getcwd(buf, (size_t)size);
while(1){
//prints users prompt
printf("\n%s@myshell:%s>", username,cwd);
//gets string from userCom line
fgets(buffer, MAX_COMMAND_SIZE + 1, stdin);
buffer[strlen(buffer)-1] = 0 ;//set null
//set-up history function
userCom.history[last% HIS_SIZE] = cmd;
last++;
//parses tokens and looks for delimiters
token[tok] = strtok(buffer,whitespace);
while(token[tok])
{
++tok;
if(tok == MAX_ARGS)
printf("Reached MAX userCom arguments");
break;
token[tok] = strtok(NULL, whitespace);
}
i =0;
//sort tokens based on special characters
for (;i<tok;++i)
{
if(!strcmp(token[i], "<"))
{
userCom.output = token[++i];
}
else if(!strcmp(token[i], ">"))
{
userCom.input = token[++i];
}
else if (token[i][0] == '$')
{
char* toktok = getenv((const char*)&token[i][1]);
if (!toktok)
{
printf("%s: ERROR: variable.\n", token[i]);
return 0;
}
else
{
userCom.arg[userCom.argument] = toktok;
++(userCom.argument);
}
}
else
{
userCom.arg[userCom.argument] = token[i];
++(userCom.argument);
}
}
tok = 0;
userCom.arg[userCom.argument] = 0;
//handles the "cd" command
if((strcmp(userCom.arg[0],"cd") == 0))
{
if (userCom.argument > 2)
printf("cd: Too many arguments\n");
// change directories if valid target and update cwd
else if (userCom.argument == 1)
{
new = chdir(cwd);
if (new != 0)
printf("%s: No such file or directory\n");
// if no argument is given, new directory should be $HOME
else
{
new = chdir(curDirect);
// get the new current working directory
size = pathconf(".", _PC_PATH_MAX);
if ((buf = (char *)malloc((size_t)size)) != NULL)
cwd = getcwd(buf, (size_t)size);
}
}
}//end "cd" function
//handles the echo command
else if(strcmp(userCom.arg[0], "echo") == 0)
{
int p;
for(p=1;p < userCom.argument; ++p)
printf("%s ", userCom.arg[p]);
}//ends echo function
//handles exit
else if(strcmp(userCom.arg[0], "exit") == 0)
{
exit(0);
}
//handles history functions
else if(strcmp(userCom.arg[0], "history") == 0)
{
int j;
for(j = last, limit = 0; userCom.history[j] != NULL && limit != HIS_SIZE ; j = (j -1)% HIS_SIZE, limit++)
printf(" %s ",userCom.history[j]);
}
else {
break;
}
}//end while 1 loop
return 0;
}//End int main
答案 0 :(得分:0)
while(token[tok])
{
++tok;
if(tok == MAX_ARGS)
printf("Reached MAX userCom arguments");
break;
token[tok] = strtok(NULL, whitespace);
}
此循环第一次中断。可能if
应该像
if(tok == MAX_ARGS) {
printf("Reached MAX userCom arguments");
break;
}
同样userCom.argument
永远不会被设置回zero
,这会导致cd ..
第一次工作。