linux - Input of dynamic size using fgets in C -

i want have string(can contain spaces) input. want dynamic allocation. structure of program this.

#include<stdio.h> #include<string.h> #include<stdlib.h> typedef struct msgclient {     int msglen;     int msgtype;     char *cp; }m1;  int main() {     m1 *m;     m=malloc(sizeof(m1));     m->msglen=5;     m->msgtype=6;     printf("enter\t");     fgets(m->cp,50,stdin);  //here     // m->cp[strlen(m->cp)]='\0';      printf("\n%d\n%d\n",m->msglen,m->msgtype);     fputs(m->cp,stdout);     return 0; } 

i want know how input. there way second argument of fgets dynamic?

use getline(3) -instead of fgets(3)- reads dynamically allocated line.

typedef struct msgclient {   ssize_t msglen;   int msgtype;   char *cp; }m1; 

then in main function

m1 *m; m=malloc(sizeof(m1)); if (!m) { perror("malloc"); exit(exit_failure); }; m->msglen=0; m->msgtype=6; m->cp = null; printf("enter\t"); fflush(stdout); size_t msgsize = 0; m->msglen = getline(&msg->cp, &msgsize, stdin); 

you might consider adding allocated size of buffer (i.e. msgsize) additional field of struct msgclient

addenda:

notice might perhaps consider using gnu readline. offers edition , completion facilities (when reading terminal).