How to read from stdin with fgets()?

here a concatenation solution:

#include <stdio.h>#include <stdlib.h>#include <string.h>#define BUFFERSIZE 10int main() {  char *text = calloc(1,1), buffer[BUFFERSIZE];  printf("Enter a message: \n");  while( fgets(buffer, BUFFERSIZE , stdin) ) /* break with ^D or ^Z */  {    text = realloc( text, strlen(text)+1+strlen(buffer) );    if( !text ) ... /* error handling */    strcat( text, buffer ); /* note a '\n' is appended here everytime */    printf("%s\n", buffer);  }  printf("\ntext:\n%s",text);  return 0;}

You have a wrong idea of what fgets returns. Take a look at this: http://www.cplusplus.com/reference/clibrary/cstdio/fgets/

It returns null when it finds an EOF character. Try running the program above and pressing CTRL+D (or whatever combination is your EOF character), and the loop will exit succesfully.

How do you want to detect the end of the input? Newline? Dot (you said sentence xD)?

Exits the loop if the line is empty(Improving code).

#include <stdio.h>#include <string.h>// The value BUFFERSIZE can be changed to customer's taste . Changes the// size of the base array (string buffer )    #define BUFFERSIZE 10int main(void){    char buffer[BUFFERSIZE];    char cChar;    printf("Enter a message: \n");    while(*(fgets(buffer, BUFFERSIZE, stdin)) != '\n')    {        // For concatenation        // fgets reads and adds '\n' in the string , replace '\n' by '\0' to         // remove the line break ./*      if(buffer[strlen(buffer) - 1] == '\n')            buffer[strlen(buffer) - 1] = '\0'; */        printf("%s", buffer);        // Corrects the error mentioned by Alain BECKER.               // Checks if the string buffer is full to check and prevent the         // next character read by fgets is '\n' .        if(strlen(buffer) == (BUFFERSIZE - 1) && (buffer[strlen(buffer) - 1] != '\n'))        {            // Prevents end of the line '\n' to be read in the first             // character (Loop Exit) in the next loop. Reads            // the next char in stdin buffer , if '\n' is read and removed, if            // different is returned to stdin             cChar = fgetc(stdin);            if(cChar != '\n')                ungetc(cChar, stdin);            // To print correctly if '\n' is removed.            else                printf("\n");        }    }    return 0;}

Exit when Enter is pressed.

#include <stdio.h>#include <stdbool.h>#include <string.h>#include <assert.h>#define BUFFERSIZE 16int main(void){    char buffer[BUFFERSIZE];    printf("Enter a message: \n");    while(true)    {        assert(fgets(buffer, BUFFERSIZE, stdin) != NULL);        // Verifies that the previous character to the last character in the        // buffer array is '\n' (The last character is '\0') if the        // character is '\n' leaves loop.        if(buffer[strlen(buffer) - 1] == '\n')        {            // fgets reads and adds '\n' in the string, replace '\n' by '\0' to             // remove the line break .            buffer[strlen(buffer) - 1] = '\0';            printf("%s", buffer);            break;        }        printf("%s", buffer);       }    return 0;}

Concatenation and dinamic allocation(linked list) to a single string.

/* Autor : Tiago Portela   Email : sapitando@gmail.com   Sobre : Compilado com TDM-GCC 5.10 64-bit e LCC-Win32 64-bit;   Obs : Apenas tentando aprender algoritimos, sozinho, por hobby. */#include <stdio.h>#include <stdlib.h>#include <stdbool.h>#include <string.h>#include <assert.h>#define BUFFERSIZE 8typedef struct _Node {    char *lpBuffer;    struct _Node *LpProxNode;} Node_t, *LpNode_t;int main(void){    char acBuffer[BUFFERSIZE] = {0};    LpNode_t lpNode = (LpNode_t)malloc(sizeof(Node_t));    assert(lpNode!=NULL);    LpNode_t lpHeadNode = lpNode;    char* lpBuffer = (char*)calloc(1,sizeof(char));    assert(lpBuffer!=NULL);    char cChar;    printf("Enter a message: \n");    // Exit when Enter is pressed/*  while(true)    {        assert(fgets(acBuffer, BUFFERSIZE, stdin)!=NULL);        lpNode->lpBuffer = (char*)malloc((strlen(acBuffer) + 1) * sizeof(char));        assert(lpNode->lpBuffer!=NULL);        strcpy(lpNode->lpBuffer, acBuffer);        if(lpNode->lpBuffer[strlen(acBuffer) - 1] == '\n')        {            lpNode->lpBuffer[strlen(acBuffer) - 1] = '\0';            lpNode->LpProxNode = NULL;            break;        }        lpNode->LpProxNode = (LpNode_t)malloc(sizeof(Node_t));        lpNode = lpNode->LpProxNode;        assert(lpNode!=NULL);    }*/    // Exits the loop if the line is empty(Improving code).    while(true)    {        assert(fgets(acBuffer, BUFFERSIZE, stdin)!=NULL);        lpNode->lpBuffer = (char*)malloc((strlen(acBuffer) + 1) * sizeof(char));        assert(lpNode->lpBuffer!=NULL);        strcpy(lpNode->lpBuffer, acBuffer);        if(acBuffer[strlen(acBuffer) - 1] == '\n')            lpNode->lpBuffer[strlen(acBuffer) - 1] = '\0';        if(strlen(acBuffer) == (BUFFERSIZE - 1) && (acBuffer[strlen(acBuffer) - 1] != '\n'))        {            cChar = fgetc(stdin);            if(cChar != '\n')                ungetc(cChar, stdin);        }        if(acBuffer[0] == '\n')        {            lpNode->LpProxNode = NULL;            break;        }        lpNode->LpProxNode = (LpNode_t)malloc(sizeof(Node_t));        lpNode = lpNode->LpProxNode;        assert(lpNode!=NULL);    }    printf("\nPseudo String :\n");    lpNode = lpHeadNode;    while(lpNode != NULL)    {        printf("%s", lpNode->lpBuffer);        lpNode = lpNode->LpProxNode;    }    printf("\n\nMemory blocks:\n");    lpNode = lpHeadNode;    while(lpNode != NULL)    {        printf("Block \"%7s\" size = %lu\n", lpNode->lpBuffer, (long unsigned)(strlen(lpNode->lpBuffer) + 1));        lpNode = lpNode->LpProxNode;    }    printf("\nConcatenated string:\n");    lpNode = lpHeadNode;    while(lpNode != NULL)    {        lpBuffer = (char*)realloc(lpBuffer, (strlen(lpBuffer) + strlen(lpNode->lpBuffer)) + 1);        strcat(lpBuffer, lpNode->lpBuffer);        lpNode = lpNode->LpProxNode;    }    printf("%s", lpBuffer);    printf("\n\n");    // Deallocate memory    lpNode = lpHeadNode;    while(lpNode != NULL)    {        lpHeadNode = lpNode->LpProxNode;        free(lpNode->lpBuffer);        free(lpNode);        lpNode = lpHeadNode;    }    lpBuffer = (char*)realloc(lpBuffer, 0);    lpBuffer = NULL;    if((lpNode == NULL) && (lpBuffer == NULL))    {        printf("Deallocate memory = %s", (char*)lpNode);    }    printf("\n\n");    return 0;}