C、 使用argv[]作为命令行参数
我在这个程序上遇到了问题,当我使用stdin时,它工作得很好,但是当我修改它以从命令行获取字符时,它就不工作了。我知道我做错了什么,但不知道是什么,任何帮助都将不胜感激 说明和代码:C、 使用argv[]作为命令行参数,c,file,argv,C,File,Argv,我在这个程序上遇到了问题,当我使用stdin时,它工作得很好,但是当我修改它以从命令行获取字符时,它就不工作了。我知道我做错了什么,但不知道是什么,任何帮助都将不胜感激 说明和代码: /* Program prints the date in this form: September 13, 2010 allow the user to enter date in either 9-13-2010 or 9/13/2010 format, otherwise print '
/* Program prints the date in this form: September 13, 2010
allow the user to enter date in either 9-13-2010 or 9/13/2010
format, otherwise print 'error' */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *month(int m)
{
char *months[]={"January","February","March","April","May",
"June", "July","August","September","October",
"November","December"};
return months[m-1];
}
int main(int argc, char *argv[])
{
int m=0,d=0,y=0;
FILE *fp;
if((fp=fopen(argv[1],"rb")) == NULL)
{
fprintf(stderr,"Couldn't open the file. ");
exit(EXIT_FAILURE);
}
printf("Type a date (mm-dd-yyyy) or (mm/dd/yyyy): \n");
if(fscanf(fp,"%d%*[/-]%d%*[/-]%d",&m,&d,&y) != 3) //store characters in variables
{
fprintf(stderr, "Not properly formatted.");
exit(EXIT_FAILURE);
}
printf("%s %2d, %4d",month(m),d,y);
return 0;
}
输出:
Couldn't open the file.
这里我们有一个通用的解决方案。可以通过文件(fscanf)、命令行(sscanf)或键入(scanf)传递日期
#包括
#包括
#包括
字符*月份(整数m)
{
字符*月份[]={“一月”、“二月”、“三月”、“四月”、“五月”,
“六月”、“七月”、“八月”、“九月”、“十月”,
“11月”、“12月”};
返回月份[m-1];
}
int main(int argc,char*argv[])
{
int m=0,d=0,y=0;
文件*fp;
int错误格式=0;
如果(argc>1)
{
if((fp=fopen(argv[1],“rb”))==NULL)
{
如果(sscanf(argv[1],%d%*[/-]%d%*[/-]%d“,&m,&d,&y)!=3)
错误格式=1;
}
其他的
{
如果(fscanf(fp,“%d%*[/-]%d%*[/-]%d”、&m、&d、&y)!=3)
错误格式=1;
}
}
其他的
{
printf(“键入日期(mm dd yyyy)或(mm/dd/yyyy):\n”);
如果(扫描频率(“%d%*[/-]%d%*[/-]%d”、&m、&d、&y)!=3)
错误格式=1;
}
如果(格式错误)
{
fprintf(stderr,“格式不正确”);
退出(退出失败);
}
printf(“%s%2d,%4d\n”,月份(m),d,y);
返回0;
}
我修改了您的程序,以解决您遇到的问题(并解决一些未定义的行为,简称“UB”),但仅此而已:
#include <stdio.h>
#include <stdlib.h>
const char *month(int m) {
const char const *months[] = {
"January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December",
};
if (1 <= m && m <= 12) {
return months[m - 1];
} else {
return NULL;
}
}
int main(int argc, char *argv[]) {
int m = 0, d = 0, y = 0;
if (argc == 2) {
if (sscanf(argv[1], "%d%*[/-]%d%*[/-]%d", &m, &d, &y) != 3) {
fprintf(stderr, "Not properly formatted.");
exit(EXIT_FAILURE);
}
printf("%s %2d, %4d", month(m), d, y);
} else {
fprintf(stderr, "Please provide one date argument to the program, formatted as mm-dd-yyyy or mm/dd/yyyy\n");
exit(EXIT_FAILURE);
}
return 0;
}
#包括
#包括
常量字符*月份(整数m){
常量字符常量*月份[]={
“一月”、“二月”、“三月”、“四月”,
“五月”、“六月”、“七月”、“八月”,
“九月”、“十月”、“十一月”、“十二月”,
};
如果(1)我使用codeblocks ide,我在程序参数窗口中键入01/30/1990,我也使用gcc运行它,它会显示“系统无法接受您输入的日期”。“客户端不拥有所需的特权”。fopen(“01/30/1999”,“rb”)
将尝试打开路径为01/30/1999
的文件。显然,不存在此类文件。argv[1]
具有未定义的行为,除非您之前确定argc
至少为两个。不要在fp
上使用fscanf
(文件-scanf
),而是使用sscanf
(字符串-scanf
)在argv[1]
上,尝试perror(argv[1])
,而不是fprintf(stderr,“无法打开文件”);
(这会产生几乎无用的错误消息),它会准确地告诉您问题所在。OP的评论显示这不是他们想要的:“如何从命令行获取输入,然后提取信息以将其放入变量中?“m、d和y都是变量。这不是重点。OP希望从命令行读取输入,而不是从命令行上指定的文件。好的,@Rhymoid。现在它也可以与命令行一起使用。谢谢您的评论,+1的回答也是正确的!”!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* month(int m)
{
char* months[] = { "January", "February", "March", "April", "May",
"June", "July", "August", "September", "October",
"November", "December" };
return months[m - 1];
}
int main(int argc, char* argv[])
{
int m = 0, d = 0, y = 0;
FILE* fp;
int wrongFormat = 0;
if (argc > 1)
{
if ((fp = fopen(argv[1], "rb")) == NULL)
{
if (sscanf(argv[1], "%d%*[/-]%d%*[/-]%d", &m, &d, &y) != 3)
wrongFormat = 1;
}
else
{
if (fscanf(fp, "%d%*[/-]%d%*[/-]%d", &m, &d, &y) != 3)
wrongFormat = 1;
}
}
else
{
printf("Type a date (mm-dd-yyyy) or (mm/dd/yyyy): \n");
if (scanf("%d%*[/-]%d%*[/-]%d", &m, &d, &y) != 3)
wrongFormat = 1;
}
if (wrongFormat)
{
fprintf(stderr, "Not properly formatted.");
exit(EXIT_FAILURE);
}
printf("%s %2d, %4d\n", month(m), d, y);
return 0;
}
#include <stdio.h>
#include <stdlib.h>
const char *month(int m) {
const char const *months[] = {
"January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December",
};
if (1 <= m && m <= 12) {
return months[m - 1];
} else {
return NULL;
}
}
int main(int argc, char *argv[]) {
int m = 0, d = 0, y = 0;
if (argc == 2) {
if (sscanf(argv[1], "%d%*[/-]%d%*[/-]%d", &m, &d, &y) != 3) {
fprintf(stderr, "Not properly formatted.");
exit(EXIT_FAILURE);
}
printf("%s %2d, %4d", month(m), d, y);
} else {
fprintf(stderr, "Please provide one date argument to the program, formatted as mm-dd-yyyy or mm/dd/yyyy\n");
exit(EXIT_FAILURE);
}
return 0;
}