[英]Can gdb print the contents of the buffer written to by the C write() function?
[英]C function, print to buffer
我有一个客户端/服务器应用程序,并且在那里出现错误-> perror(“ [服务器]无法将消息发送到客户端。\\ n“)。 因此服务器无法发送msgrasp(缓冲区)。 如果可以的话,我将不胜感激。
void printdir(char *dir, int depth)
{
DIR *dp;
struct dirent *entry;
struct stat statbuf;
if((dp = opendir(dir)) == NULL) {
fprintf(stderr,"cannot open directory: %s\n", dir);
return;
}
chdir(dir);
while((entry = readdir(dp)) != NULL) {
lstat(entry->d_name,&statbuf);
if(S_ISDIR(statbuf.st_mode)) {
/* Found a directory, but ignore . and .. */
if(strcmp(".",entry->d_name) == 0 ||
strcmp("..",entry->d_name) == 0)
continue;
printf("%*s%s/\n",depth,"",entry->d_name);
/* Recurse at a new indent level */
printdir(entry->d_name,depth+4);
}
else printf("%*s%s\n",depth,"",entry->d_name);
}
chdir("..");
closedir(dp);
}
int printForClient(int fd)
{
char buffer[100];
int bytes;
char msg[100];
char *msgrasp=NULL;
bytes = read (fd, msg, sizeof (buffer));
if (bytes < 0)
{
perror ("Can't read from client.\n");
return 0;
}
printf ("[server]..%s\n", msg);
printdir(&msgrasp,msj,0);
printf("[server]%s\n",msgrasp);
if (bytes && write (fd, msgrasp, bytes) < 0)
{
perror ("[server] Can't send the message to client.\n");
return 0;
}
return bytes;
}
我建议添加一个char *类型的参数(一个指向char数组的指针),并在每次递归时都使指针前进。 我的尝试(假设缓冲区对于输出来说足够长):
void printdir(char *dir, int depth, char* output)
{
DIR *dp;
struct dirent *entry;
struct stat statbuf;
char tmp[100];
if((dp = opendir(dir)) == NULL) {
fprintf(stderr,"cannot open directory: %s\n", dir);
return;
}
chdir(dir);
while((entry = readdir(dp)) != NULL) {
lstat(entry->d_name,&statbuf);
if(S_ISDIR(statbuf.st_mode)) {
/* Found a directory, but ignore . and .. */
if(strcmp(".",entry->d_name) == 0 ||
strcmp("..",entry->d_name) == 0)
continue;
sprintf(tmp, "%*s%s/\n",depth,"",entry->d_name);
strcpy(buffer, tmp);
/* Recurse at a new indent level */
printdir(entry->d_name,depth+4, buffer+strlen(tmp));
}
else printf("%*s%s\n",depth,"",entry->d_name);
}
chdir("..");
closedir(dp);
}
int main()
{ char buffer[1000]; //buffer for printdir output.
printf("Directory scan of /home:\n");
printdir("/home",0);
printf("done.\n");
exit(0);
}
您可能希望在每次执行之间添加\\n
,这取决于您希望对输出执行的操作。 请注意,在此程序中,每个字符串末尾的\\0
被删除。
这不是一个很好的主意,但是由于这是您在此处所要求的,因此您有了动态内存分配的解决方案
#include <stdio.h>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
void printdir(char **output, const char *const dir, int depth)
{
DIR *dp;
struct dirent *entry;
struct stat statbuf;
if ((dp = opendir(dir)) == NULL)
{
fprintf(stderr,"cannot open directory: %s\n", dir);
return;
}
chdir(dir);
while ((entry = readdir(dp)) != NULL)
{
/* check if stat succeeded */
if (lstat(entry->d_name, &statbuf) == -1)
continue;
if (S_ISDIR(statbuf.st_mode) != 0)
{
char *buffer;
size_t length;
/* Found a directory, but ignore . and .. */
if(strcmp(".",entry->d_name) == 0 ||
strcmp("..",entry->d_name) == 0)
continue;
length = 4 + depth + strlen(entry->d_name);
if (*output != NULL)
length += strlen(*output);
buffer = realloc(*output, length);
if (buffer != NULL)
{
char current[length];
if (*output == NULL)
buffer[0] = '\0';
*output = buffer;
snprintf(current, length, "%*s%s/\n", depth, " ", entry->d_name);
strcat(*output, current);
//printf("%*s%s/\n",depth,"",entry->d_name);
/* Recurse at a new indent level */
}
else
{
fprintf(stderr, "Out of memory\n");
free(*output);
*output = NULL;
closedir(dp);
return;
}
printdir(output, entry->d_name, depth + 4);
}
else
{
char *buffer;
size_t length;
length = 4 + depth + strlen(entry->d_name);
if (*output != NULL)
length += strlen(*output);
buffer = realloc(*output, length);
if (buffer != NULL)
{
char current[length];
if (*output == NULL)
buffer[0] = '\0';
*output = buffer;
snprintf(current, length, "%*s%s/\n", depth, " ", entry->d_name);
strcat(*output, current);
}
else
{
fprintf(stderr, "Out of memory\n");
free(*output);
*output = NULL;
closedir(dp);
return;
}
}
}
chdir("..");
closedir(dp);
}
int main()
{
char *buffer = NULL; //buffer for printdir output.
printf("Directory scan of /home:\n");
printdir(&buffer, "/home", 0);
printf("done.\n");
printf("%s\n", buffer);
free(buffer);
exit(0);
}
这不是一个好主意,因为您不知道是否有足够的内存来容纳所有文本,它可能会增长很多,我在这段代码中针对这种情况添加了检查,以防出现内存不足的情况,此函数将中止读取,释放资源并返回。
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