今天在写父子进程用两个单向管道通信时，出现了错误：
打开core文件发现：
附上源码：
1 #include <stdlib.h> 2 #include <unistd.h> 3 #include <stdio.h> 4 #include <sys/wait.h> 5 #include <errno.h> 6 #include <string.h> 7 8 void erreur(const char *msg) 9 { 10 perror(msg); 11 } 12 13 #define NBCAR 256 14 15 int main(void) 16 { 17 pid_t pid; 18 int tube[2]; 19 int tube2[2]; 20 int ret_out, ret_in; 21 char *buffer,*buffer2; 22 23 if (pipe(tube) == -1) {//from parent to son 24 erreur("Erreur de creation du pipe"); 25 exit(EXIT_FAILURE); 26 } 27 if (pipe(tube2) == -1) {//from son to parent 28 erreur("Erreur de creation du pipe"); 29 exit(EXIT_FAILURE); 30 } 31 buffer = (char *) malloc(NBCAR * sizeof(char)); 32 buffer2 = (char *) malloc(NBCAR * sizeof(char)); 33 switch (pid = fork()) { 34 case (pid_t) -1: 35 erreur("fork"); 36 case (pid_t) 0: 37 close(tube[1]); 38 close(tube2[0]); 39 if (printf("Je suis le fils de PID %d\n write dans le tube : %s\n Nbr Caracteres lus: %d\n",getpid(), buffer, ret_in =write(tube2[1], buffer="tube1 s to p", NBCAR - 1)) == -1) { 40 erreur(" Pb Lecture "); 41 exit(EXIT_FAILURE); 42 } 43 if (printf("Je suis le fils de PID %d\n Lecture dans le tube : %s\n Nbr Caracteres lus: %d\n",getpid(), buffer2, ret_in =read(tube[0], buffer2, NBCAR - 1)) == -1) { 44 erreur(" Pb Lecture "); 45 exit(EXIT_FAILURE); 46 } 47 48 exit(0); 49 break; 50 default: 51 close(tube[0]); 52 close(tube2[1]); 53 if (printf("Je suis le parent de PID %d\n Lecture dans le tube : %s\n Nbr Caracteres lus: %d\n",getpid(), buffer, ret_in =read(tube2[0], buffer, NBCAR - 1)) == -1) { 54 erreur(" Pb Lecture "); 55 exit(EXIT_FAILURE);} 56 if (printf("Je suis le parent de PID %d\n write dans le tube : %s\n Nbr Caracteres lus: %d\n",getpid(), buffer2, ret_in =write(tube[1], buffer2="tube2 p to s", NBCAR - 1)) == -1) { 57 erreur(" Pb Lecture "); 58 exit(EXIT_FAILURE);} 59 60 wait(NULL); 61 break; 62 63 } 64 free(buffer); 65 free(buffer2); 66 return EXIT_SUCCESS; 67 }
SIGSEGV --- Segment Fault. The possible cases of your encountering this error are:
1.buffer overflow --- usually caused by a pointer reference out of range.
2.stack overflow --- please keep in mind that the default stack size is 8192K.
3.illegal file access --- file operations are forbidden on our judge system.
后来通过邮件问老师，发现是buffer出现内存泄漏。
先梳理一下C语言中char和字符型、字符串型、单引号、双引号、字符串截止符号的概念：
首先C中没有专门的字符串变量（没有C++中的String类），单个的char就代表一个字符，赋值时应该是：char c = ‘a‘; 故而单引号表示单个字符。如果用char表示字符串，需要定义char的数组，并有两种主要赋值方法：
char greeting[6] = {‘H‘, ‘e‘, ‘l‘, ‘l‘, ‘o‘, ‘\0‘}; char greeting[] = "Hello"; //第二例子 char c[10]={‘I‘, ‘ ‘, ‘a‘, ‘m‘, ‘ ‘, ‘h‘, ‘a‘, ‘p‘, ‘p‘, ‘y‘}; char c[]="I am happy";
第一种方法：若初值个数小于数组长度,则只将这些字符赋绐数组中前面的元素,其余元素自动定为空字符(即‘\0‘)。
第二种方法：编译器会在初始化数组时，自动把 ‘\0‘ 放在字符串的末尾。
回过头看代码中对buffer的操作：
对buffer和buffer2都分配了256个字节的空间（注意他们是指针，指向256个字节连续空间的首地址），但在赋值时直接对buffer使用等号=，把常量字符串赋给一个指针本身，这显然是不对的····原来分配的两块256字节的内存现在没有指针指向了，最后free的时候并不能把他们释放掉，因此造成内存泄漏
但write()和read()中间参数又必须是指针，这时就需要strcpy(）函数，改成：
buffer=strcpy(buffer,"tube1 s to p") buffer2=strcpy(buffer2,"tube2 p to s")
完美运行，不会报错
借此机会再复习一下char字符串用等号=赋值和用strcpy()赋值的区别：
等号赋值，两个char指向同一个空间
函数赋值，两个char各有一个相同的字符串拷贝
本文完
参考:
https://blog.csdn.net/yal179/article/details/13019817
https://www.runoob.com/cprogramming/c-strings.html
http://www.voidcn.com/article/p-wlesexyc-ben.html
https://zhidao.baidu.com/question/53110127.html
https://www.runoob.com/cprogramming/c-function-strcpy.html
SIGSEGV错误
https://blog.csdn.net/brace/article/details/1102422
关于core dumped
https://blog.51cto.com/xjsunjie/1954870
https://blog.csdn.net/peiyao456/article/details/70045195
由Linux中管道的buffer，浅谈C语言中char类型字符串拷贝使用strcpy()和=赋值符号的区别
原文：https://www.cnblogs.com/mrlonely2018/p/11710905.html