/* chicken_sh.c
* 破壳，小鸡.
* 增加了命令行处理，比egg_sh好用了
*/
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<signal.h>
#include "smsh.h"
#define DFL_PROMPT "> "
void setup();
void fatal(char *s1, char *s2, int n)
int main()
{
char *cmdline, *prompt, **arglist;
int result;
prompt = DFL_PROMPT;
setup();
while ((cmdline = next_cmd(prompt, stdin)) != NULL) {
if ((arglist = splitline(cmdline)) != NULL) {
result = execute(arglist);
freelist(arglist);
}
free(cmdline);
}
return 0;
}
void setup()
/* 设置信号处理函数
*/
{
signal(SIGINT, SIG_IGN);
signal(SIGQUIT, SIG_IGN);
}
void fatal(char *s1, char *s2, int n)
/* 错误处理函数
*/
{
fprintf(stderr, "Error: %s, %s\n", s1, s2);
exit(n);
}
gcc -o chichen_sh chicken_sh.c splitline.c execute.c
/*splitline.c
* 为chicken_sh读取并解析命令
*char *next_cmd(char *prompt, FILE *fp) 取下一条指令
*char **splitline(char *str); 解析字符串
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include "chicken_sh.h"
char *next_cmd(char *prompt, FILE * fp)
{
char *buf;
int bufspace = 0;
int pos=0; /* 当前位置 */
int c;
printf("%s", prompt);
while ((c = getc(fp)) != EOF) {
/*若需要空间*/
if (pos + 1 >= bufspace) {
if (bufspace == 0)
buf = emalloc(BUFSIZ);
else
buf = erealloc(buf, bufspace + BUFSIZ); /* 扩大分配的内存 */
bufspace += BUFSIZ;
}
/* 命令结束 */
if (c == ‘\n‘)
break;
/* 如果不结束，则添加进缓冲区 */
buf[pos++] = c;
}
if (c == EOF && pos == 0)
return NULL;
buf[pos] = ‘\0‘;
return buf;
}
#define is_delim(x) ((x) == ‘ ‘ || (x) == ‘\t‘) /*参数分隔符是空格或tab*/
char *newstr(char *s, int l);
char **splitline(char *line)
{
char **args; /*要返回的参数数组*/
int spots = 0; /*参数指针的容量*/
int bufspace = 0; /*缓冲空间*/
int argnum = 0; /*参数计数*/
char *cp = line;
char *start;
int len;
if (line == NULL) /* 什么输入也没有 */
return NULL;
args = emalloc(BUFSIZ); /* 分配参数数组 */
bufspace = BUFSIZ;
spots = BUFSIZ / sizeof(char *);
while (*cp != ‘\0‘) {
while (is_delim(*cp))
cp++;
if (*cp == "\0")
break;
/* 确保参数数组的空间 */
if (argnum + 1 >= spots) {
args = erealloc(args, bufspace + BUFSIZ);
bufspace += BUFSIZ;
spots += (BUFSIZ / sizeof(char *));
}
/* 标记开始的地方，查找以\0 结束的位置 */
start = cp;
len = 1;
while (*++cp != ‘\0‘ && !(is_delim(*cp)))
len++;
args[argnum++] = newstr(start, len);
}
args[argnum] = NULL;
return args;
}
/*
* 构造字符串，以‘\0‘ 结尾*/
char *newstr(char *s, int l)
{
char *rv = emalloc(l + 1);
rv[l] = ‘\0‘;
strncpy(rv, s, l);
return rv;
}
void freelist(char **list)
/*参数用完后，释放空间*/
{
char **cp = list;
while (*cp)
free(*cp++);
free(list);
}
void *emalloc(size_t n)
{
void *rv;
if ((rv = malloc(n)) == NULL)
fatal("out of memory", "", 1);
return rv;
}
void *erealloc(void *p, size_t n)
{
void *rv;
if ((rv = realloc(p, n)) == NULL)
fatal("realloc() failed", "", 1);
return rv;
}
if cat hello.c then echo hello fi
学习理解shell的好办法--编写自己的shell 之二,布布扣,bubuko.com
原文：http://my.oschina.net/sukai/blog/296565