#include<string.h>
#include<malloc.h>
main()
{ char *s,*h,*tint l
s=(char*)malloc(20*sizeof(char))
printf("input a string:")
scanf("%s",s)
l=strlen(s)/*求字符串长度赋给l*/
h=st=s+l-1/*h指针指向第一个字符，t指向最后一个*/
for(h<th++,t--) /*从头尾向中比较*/
{if((*h)!=(*t)){printf("not symmetric")break} /*发现不同的字符，显示不对称，并结束比较*/
}if(h>=t)printf("symmetric")/*如果比较完了，则显示对称*/
getch()
}
2.#include<stdio.h>
#include<string.h>
#include<malloc.h>
main()
{ char *s,*p,*q
s=(char*)malloc(20*sizeof(char))
printf("input string:")
scanf("%s",s)
p=s
while(*p)
{if(*p=='a'||*p=='e'||*p=='i'||*p=='o'
||*p=='u')
{q=p/*让q指针和q指针指向同一个字符*/
while(*q)
{*q=*(q+1)q++} /*将当前字符后面的字符前移，相当于把p指着的当前字符删除*/
p--}
p++}
printf("%s",s)
getch()
}
3.#include<stdio.h>
#include<string.h>
main()
{ int a,i=0,s=0char b[52],c[100],t
for(t='A't<='Z't++)
b[i++]=t
for(t='a't<='z't++)
b[i++]=t
for(i=0i<52i++)
printf("%c",b[i])/*将52个大小写字母存入数组b中*/
srand(time(NULL))/*使每次随机产生的数不同*/
for(i=0i<100i++) /*循环100次，产生100个随机字母*/
{ a=rand()%51/*每次从0到51中产生一个随机数，从而从b〔0〕到b〔51〕中选出一个字母*/
c[i]=b[a]/*每次产生的随机字母存入数组c中*/
if(b[a]=='a'||b[a]=='e'||b[a]=='i'||
b[a]=='o'||b[a]=='u'||b[a]=='A'||
b[a]=='E'||b[a]=='I'||b[a]=='O'||b[a]
=='U')s++/*当是元音字母时，用s来统计个数*/
}
printf("\n")
for(i=0i<100i++)printf("%c ",c[i])
printf("\ns:%d",s)
getch()
}
/*Name: list.c
Author: guozan _SCS_BUPT
Mail: guozan523@foxmail.com
Date: 2010/4/6
实验目的：练习vi，使用UNIX的系统调用和库函数，体会UNIX文件通配符的处理方式以及命令对选项的处理方式。
编程实现程序list.c，列表普通磁盘文件(不考虑目录和设备文件等)，列出文件名和文件大小。
与ls命令类似，命令行参数可以有0到多个
0个参数：列出当前目录下所有文件
参数为普通文件：列出文件
参数为目录：列出目录下所有文件
实现自定义选项r,a,l,h,m以及--
r 递归方式列出子目录
a 列出文件名第一个字符为圆点的普通文件（默认情况下不列出文件名首字符为圆点的文件）
l 后跟一整数，限定文件大小的最小值（字节）
h 后跟一整数，限定文件大小的最大值（字节）
m 后跟一整数n，限定文件的最近修改时间必须在n天内
-- 显式地终止命令选项分析
*/
#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
/*
slective options about ls
rflag is about recursive
aflag is about ones with . infront
lflag is about the minimum size
hflag is about the maximum size
mflag is about the modified time
*/
int rflag, aflag, lflag, hflag, mflag
long modified_time //the last time file be modified, days ago
off_t lower_size //file's minimum size
off_t upper_size //file's maximum size
/*
set the flags, thus the ls option
*/
void getoptions(int argc, char *argv[])
{
char ch
//clear, all unseted
rflag = 0aflag = 0lflag = 0hflag = 0mflag = 0
//use getopt to get the options, want to know more, call man
//the last one or after -- was set in argv[optind]
while ((ch = getopt(argc, argv, "ral:h:m:")) != -1) {
switch (ch) {
case 'r': rflag = 1break
case 'a': aflag = 1break
case 'l': lflag = 1lower_size = atol(optarg)break
case 'h': hflag = 1upper_size = atol(optarg)break
case 'm': mflag = 1modified_time = atol(optarg)break //get days
case '?': printf("Unknown option: %c\n", (char)optopt)break
default : printf("Step into default\n")break
}
}
}
/*
the function to list things in path
*/
int ls(char *path)
{
struct stat st //for check this is a directory or file
char temp[100] //if path is null, it is used to get current directory
// get the path
if (path == NULL || path[0] == '-') {
path = temp
getcwd(path, 100)
}
/* open the inode of file */
if (lstat(path, &st)) {
fprintf(stderr, "Error: %s not exist.\n", path)
return (-1)
}
/* judge whether the file is a file or a directory */
if (S_ISDIR(st.st_mode)) {
ls_dir(path)
}
else if (S_ISREG(st.st_mode)) {
print(path)
}
else {
printf("Not ordinary file, wouldn't be listed.\n")
}
return 0
}
/*
list dirs, may recursively or not, depending on rflag
one thing is sure that it will list directories and files first,
then consider the things in the directories
*/
int ls_dir(char *path)
{
DIR *dp = NULL
struct dirent *dirp = NULL
if (path[0] != '.' || (path[0] == '.' &&aflag == 1)) {
printf("\n%s:\n****************************************\n", path)
/* open the directory */
if ((dp = opendir(path)) == NULL) {
fprintf(stderr, "Error: can't open directory %s!\n", path)
return (-1)
}
chdir(path)
/* list all the things in directory */
while ((dirp = readdir(dp)) != NULL) {
print(dirp->d_name)
}
/* recursively ls dirs, after ls things together,
it's time to list things in children directory */
if (rflag == 1) {
rewinddir(dp) //reset dp
while ((dirp = readdir(dp)) != NULL) {
if (strcmp(dirp->d_name, ".") == 0
|| strcmp(dirp->d_name, "..") == 0) {//no current and parent directory
continue
}
ls_dir_r(dirp->d_name) //only list directories, judged inside the function
}
}
/* close the directory */
if (closedir(dp)) {
fprintf(stderr, "Error: can't close the directory %s!\n", path)
return -1
}
chdir("..")
}
return 0
}
/*
list directories recursively,
only directories, nomatter what path you put in
*/
int ls_dir_r(char *path)
{
struct stat st
/* open the inode of file */
if (lstat(path, &st)) {
fprintf(stderr, "Error: %s not exist.\n", path)
return (-1)
}
/* only ls directories */
if (S_ISDIR(st.st_mode)) {
ls_dir(path)
}
}
/*
print the filetype/size/name on the screen
*/
int print(char *path)
{
struct stat st
time_t tp
char *filename = NULL
//get current time
time(&tp)
if (lstat(path, &st)) {
fprintf(stderr, "Error: %s can't be opened.\n", path)
return (-1)
}
/* get file name */
if ((filename = strrchr(path, '/')) != NULL) {
filename++
}
else {
filename = path
}
/* judge whether to list the file */
if ((S_ISDIR(st.st_mode)|| S_ISREG(st.st_mode))//only directories and normal files
&&(lflag == 0 || (lflag == 1 &&(st.st_size >= lower_size))) //the min size
&&(hflag == 0 || (hflag == 1 &&(st.st_size <= upper_size))) //the max size
&&(mflag == 0 || (mflag == 1 &&((tp - st.st_mtime) <= modified_time * 24 * 60 * 60)))//modified time
&&(aflag == 1 || (aflag == 0 &&filename[0] != '.'))//file with a '.' infront
) {
printf("%s\t%10ld\t%s\n", (S_ISDIR(st.st_mode) ? "DIR": "FILE"), st.st_size, filename)
}
return 0
}
/*
The main function
*/
int main(int argc, char *argv[])
{
getoptions(argc, argv)
ls(argv[optind])
return 0
}
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