[英]How to concat two char * in C?
I receive a char * buffer which have the lenght of 10. But I want to concat the whole content in my struct which have an variable char *. 我收到一个char *缓冲区,其长度为10.但是我想在我的struct中连接整个内容,它们有一个变量char *。
typedef struct{
char *buffer;
//..
}file_entry;
file_entry real[128];
int fs_write(char *buffer, int size, int file) {
//every time this function is called buffer have 10 of lenght only
// I want to concat the whole text in my char* in my struct
}
Something like this : 像这样的东西:
real[i].buffer += buffer;
How can I do this in C ? 我怎么能在C中这样做?
In general, do the following (adjust and add error checking as you see fit) 通常,请执行以下操作(根据需要调整并添加错误检查)
// real[i].buffer += buffer;
// Determine new size
int newSize = strlen(real[i].buffer) + strlen(buffer) + 1;
// Allocate new buffer
char * newBuffer = (char *)malloc(newSize);
// do the copy and concat
strcpy(newBuffer,real[i].buffer);
strcat(newBuffer,buffer); // or strncat
// release old buffer
free(real[i].buffer);
// store new pointer
real[i].buffer = newBuffer;
You can use strcat(3)
to concatenate strings. 您可以使用
strcat(3)
来连接字符串。 Make sure you have allocated enough space at the destination! 确保您在目的地分配了足够的空间!
Note that just calling strcat()
a bunch of times will result in a Schlemiel the Painter's algorithm . 请注意,只是多次调用
strcat()
将导致Schlemiel成为Painter的算法 。 Keeping track of the total length in your structure (or elsewhere, if you prefer) will help you out with that. 跟踪您的结构(或其他地方,如果您愿意)的总长度将帮助您解决这个问题。
I am not clear. 我不清楚。 Do you want:
你想要:
real[0].buffer
, or real[0].buffer
,或者 real[i].buffer
, or real[i].buffer
,或者 You will need to allocate enough space for the copy of the buffer: 您需要为缓冲区的副本分配足够的空间:
#include <stdlib.h>
//...
int size = 10+1; // need to allocate enough space for a terminating '\0'
char* buff = (char *)malloc(size);
if (buff == NULL) {
fprintf(stderr, "Error: Failed to allocate %d bytes in file: %s, line %d\n,
size, __FILE__, __LINE__ );
exit(1);
}
buff[0] = '\0'; // terminate the string so that strcat can work, if needed
//...
real[i].buffer = buff; // now buffer points at some space
//...
strncpy(real[i].buffer, buffer, size-1);
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