我正在创建一个shell，它有一些用于执行自定义函数的bulit-in命令。但是，当我尝试两次调用相同的命令时会出现问题。
第一次执行没有问题，正确执行我的功能。但是，在第一次执行完成后，当我使用不同的选项集再次执行该命令时，除了runALS print语句之外，它不执行任何操作。发生了什么，如何解决？
如何执行：runALS -FCFS或runALS -SJF
自定义函数：fcfs()和sjf()
输出：
--WELCOME TO ALS--
Please enter:
> runALS -FCFS
runALS
.... // normal output for fcfs()
Please enter:
> Please enter:
> runALS -SJF
runALS
// no output for sjf()
另一个执行：
--WELCOME TO ALS--
Please enter:
> runALS -SJF
runALS
.... // normal output for sjf()
Please enter:
> Please enter:
> runALS -FCFS
runALS
// no output for fcfs()
当前代码：
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
/*
Function Declarations for builtin shell commands:
*/
int lsh_addOrder(char **args);
int lsh_runALS(char **args);
int lsh_printSchedule(char **args);
int lsh_printReport(char **args);
int lsh_endProgram(char **args);
char *builtin_str[] = {
"addOrder",
"runALS",
"printSchedule",
"printReport",
"endProgram"
};
int (*builtin_func[]) (char **) = {
&lsh_addOrder,
&lsh_runALS,
&lsh_printSchedule,
&lsh_printReport,
&lsh_endProgram
};
int lsh_num_builtins() {
return sizeof(builtin_str) / sizeof(char *);
}
/*
Builtin function implementations.
*/
/**
@brief Bultin command: create order.
@param args List of args. args[0] is "addOrder". args[1] is the "R0001". args[2] is start date "D001". args[3] is finish date. args[4] is product name. args[5] is number of product ordered
@return Always returns 1, to continue executing.
*/
int lsh_addOrder(char **args)
{
printf("addOrder\n");
return 1;
}
int lsh_printSchedule(char **args)
{
printf("printSchedule\n");
return 1;
}
int lsh_printReport(char **args)
{
printf("printReport\n");
return 1;
}
/**
@brief Builtin command: print help.
@param args List of args. Not examined.
@return Always returns 1, to continue executing.
*/
int lsh_runALS(char **args)
{
int i;
printf("runALS\n");
//printf("Type program names and arguments, and hit enter.\n");
//printf("The following are built in:\n");
//for (i = 0; i < lsh_num_builtins(); i++) {
//printf(" %s\n", builtin_str[i]);
//}
int opt;
while ((opt = getopt(2, args, "F:S:")) != -1) {
switch (opt) {
case 'F':
fcfs();
break;
case 'S':
sjf();
break;
default: /* '?' */
fprintf(stderr, "Unsupported option\n");
exit(EXIT_FAILURE);
}
}
return 1;
}
/**
@brief Builtin command: exit.
@param args List of args. Not examined.
@return Always returns 0, to terminate execution.
*/
int lsh_endProgram(char **args)
{
printf("Bye-bye!");
return 0;
}
/**
@brief Launch a program and wait for it to terminate.
@param args Null terminated list of arguments (including program).
@return Always returns 1, to continue execution.
*/
int lsh_launch(char **args)
{
pid_t pid;
int status;
pid = fork();
if (pid == 0) {
// Child process
if (execvp(args[0], args) == -1) {
perror("lsh");
}
exit(EXIT_FAILURE);
} else if (pid < 0) {
// Error forking
perror("lsh");
} else {
// Parent process
do {
waitpid(pid, &status, WUNTRACED);
} while (!WIFEXITED(status) && !WIFSIGNALED(status));
}
return 1;
}
/**
@brief Execute shell built-in or launch program.
@param args Null terminated list of arguments.
@return 1 if the shell should continue running, 0 if it should terminate
*/
int lsh_execute(char **args)
{
int i;
if (args[0] == NULL) {
// An empty command was entered.
return 1;
}
for (i = 0; i < lsh_num_builtins(); i++) {
if (strcmp(args[0], builtin_str[i]) == 0) {
return (*builtin_func[i])(args);
}
}
return lsh_launch(args);
}
#define LSH_RL_BUFSIZE 1024
/**
@brief Read a line of input from stdin.
@return The line from stdin.
*/
char *lsh_read_line(void)
{
int bufsize = LSH_RL_BUFSIZE;
int position = 0;
char *buffer = malloc(sizeof(char) * bufsize);
int c;
if (!buffer) {
fprintf(stderr, "lsh: allocation error\n");
exit(EXIT_FAILURE);
}
while (1) {
// Read a character
c = getchar();
// If we hit EOF, replace it with a null character and return.
if (c == EOF || c == '\n') {
buffer[position] = '\0';
return buffer;
} else {
buffer[position] = c;
}
position++;
// If we have exceeded the buffer, reallocate.
if (position >= bufsize) {
bufsize += LSH_RL_BUFSIZE;
buffer = realloc(buffer, bufsize);
if (!buffer) {
fprintf(stderr, "lsh: allocation error\n");
exit(EXIT_FAILURE);
}
}
}
}
#define LSH_TOK_BUFSIZE 64
#define LSH_TOK_DELIM " \t\r\n\a"
/**
@brief Split a line into tokens (very naively).
@param line The line.
@return Null-terminated array of tokens.
*/
char **lsh_split_line(char *line)
{
int bufsize = LSH_TOK_BUFSIZE, position = 0;
char **tokens = malloc(bufsize * sizeof(char*));
char *token, **tokens_backup;
if (!tokens) {
fprintf(stderr, "lsh: allocation error\n");
exit(EXIT_FAILURE);
}
token = strtok(line, LSH_TOK_DELIM);
while (token != NULL) {
tokens[position] = token;
position++;
if (position >= bufsize) {
bufsize += LSH_TOK_BUFSIZE;
tokens_backup = tokens;
tokens = realloc(tokens, bufsize * sizeof(char*));
if (!tokens) {
free(tokens_backup);
fprintf(stderr, "lsh: allocation error\n");
exit(EXIT_FAILURE);
}
}
token = strtok(NULL, LSH_TOK_DELIM);
}
tokens[position] = NULL;
return tokens;
}
/**
@brief Loop getting input and executing it.
*/
void lsh_loop(void)
{
char *line;
char **args;
int status;
do {
printf("Please enter:\n> ");
line = lsh_read_line();
args = lsh_split_line(line);
status = lsh_execute(args);
free(line);
free(args);
} while (status);
}
int fcfs(){
...
return 0;
}
int sjf(){
...
return 0;
}
/**
@brief Main entry point.
@param argc Argument count.
@param argv Argument vector.
@return status code
*/
int main(int argc, char **argv)
{
// Load config files, if any.
printf(" --WELCOME TO ALS-- \n");
// Run command loop.
lsh_loop();
// Perform any shutdown/cleanup.
return EXIT_SUCCESS;
}
答案 0 :(得分：1)
|__ (user_id)使用一些需要重置的静态变量才能再次解析相同的字符串。
[static]变量
getopt()是要处理的下一个元素的索引 在argv。系统将此值初始化为1.调用者可以 将其重置为1以重新开始扫描相同的argv或扫描时 一个新的参数向量。
所以：
optind