程序的标准输出字节长度有限制吗？

#include
#include
#include
#include

int main()
{
FILE *read_fp;
char buffer[BUFSIZ + 1];
char chars_read;

    memset(buffer, '\0', sizeof(buffer));

    read_fp = popen("ps ax", "r");

    if(read_fp != NULL)
    {
            chars_read = fread(buffer, sizeof(char), 128, read_fp);

            while(chars_read > 0)
            {
                    printf("%s", buffer);
                    chars_read = fread(buffer, sizeof(char), 128, read_fp);
            }

            pclose(read_fp);
            //printf("success\n");
            exit(EXIT_SUCCESS);
    }
    printf("failed\n");
    exit(EXIT_FAILURE);

}

这是源码1，无法进入while循环

#include
#include
#include
#include

int main()
{
FILE *read_fp;
char buffer[BUFSIZ + 1];
char chars_read;

    memset(buffer, '\0', sizeof(buffer));

    read_fp = popen("ps ax", "r");

    if(read_fp != NULL)
    {
            chars_read = fread(buffer, sizeof(char), 127, read_fp);

            while(chars_read > 0)
            {
                    printf("%s", buffer);
                    chars_read = fread(buffer, sizeof(char), 127, read_fp);
            }

            pclose(read_fp);
            //printf("success\n");
            exit(EXIT_SUCCESS);
    }
    printf("failed\n");
    exit(EXIT_FAILURE);

}

这是源码2，可以进入循环。

菜鸟在学习管道，遇到点问题，求高手。。。

没有限制，但是标准控制台输出的缓冲区有限制。