标准I/O库

#include <apue.h>
#include <error.h>

int main(void){
    int c;
    while((c=getc(stdin))!=EOF)
        if(putc(c,stdout) == EOF){
            err_sys("output error");
        }

    if(ferror(stdin)){
        err_sys("input error");
    }

    exit(0);
}

#include <apue.h>
#include <error.h>

int main(void) {
    char buf[MAXLINE];

    while (fgets(buf, MAXLINE, stdin) != NULL) {
        if (fputs(buf, stdout) == EOF) {
            err_sys("output error");
        }
    }

    if (ferror(stdin)) {
        err_sys("input error");
    }

    exit(0);
}

#include <apue.h>
#include <error.h>

void pr_stdio(const char *, FILE *);

int is_unbuffered(FILE *);

int is_linebuffered(FILE *);

int buffer_size(FILE *);

int main(void) {
    FILE *fp;
    fputs("enter any character\n", stdout);
    if (getchar() == EOF) {
        err_sys("getchar error");
    }
    fputs("one line to standard error\n", stderr);
    pr_stdio("stdin", stdin);
    pr_stdio("stdout", stdout);
    pr_stdio("stderr", stderr);

    if ((fp = fopen("/etc/passwd", "r")) == NULL) {
        err_sys("fopen error");
    }
    if (getc(fp) == EOF) {
        err_sys("getc error");
    }
    pr_stdio("/etc/passwd", fp);
    exit(0);
}

void pr_stdio(const char *name, FILE *fp) {
    printf("stream = %s, ", name);
    if (is_unbuffered(fp))
        printf("unbuffered");
    else if (is_linebuffered(fp))
        printf("line buffered");
    else
        printf("fully buffered");
    printf(", buffer size = %d\n", buffer_size(fp));
}

#if defined(_IO_UNBUFFERED)

int is_unbuffered(FILE* fp){
    return(fp->_flags & _IO_UNBUFFERED);
}

int is_linebuffered(FILE *fp){
    return(fp->_flags & _IO_LINE_BUF);
}

int buffer_size(FILE *fp){
    return(fp->_IO_buf_end - fp->_IO_buf_base);
}

#elif defined(__SNBF)

int is_unbuffered(FILE *fp) {
    return (fp->_flags & __SNBF);
}

int is_linebuffered(FILE *fp) {
    return (fp->_flags & __SLBF);
}

int buffer_size(FILE *fp) {
    return (fp->_bf._size);
}

#elif defined(__IONBF)

//some

#else
#error unknown stdio implementation!
#endif

#include <apue.h>
#include <error.h>

int main(void) {
    char name[L_tmpnam], line[MAXLINE];
    FILE *fp;
    printf("%s\n", name);
    if ((fp = tmpfile()) == NULL)
        err_sys("tmpfile error");
    fputs("one line of output\n", fp);
    rewind(fp);
    if (fgets(line, sizeof(line), fp) == NULL)
        err_sys("fgets error");
    fputs(line, stdout);
    exit(0);
}

#include <apue.h>
#include <error.h>

void make_temp(char *template);

int main() {
    char good_template[] = "/tmp/dirXXXXXX";
    char *bad_template = "/tmp/dirXXXXXX";
    printf("trying to create first temp file ...\n");
    make_temp(good_template);
    printf("trying to create second temp file ...\n");
    make_temp(bad_template);
    exit(0);
}

void make_temp(char *template) {
    int fd;
    struct stat sbuf;
    if ((fd = mkstemp(template)) < 0)
        err_sys("can't create temp file");
    printf("temp name = %s\n", template);
    close(fd);
    if (stat(template, &sbuf) < 0) {
        if (errno == ENOENT)
            printf("file doesn't exist\n");
        else
            err_sys("stat failed");

    } else {
        printf("file exists\n");
        unlink(template);
    }
}

#include <apue.h>
#include <error.h>

#define BSZ 48

int main() {
    FILE *fp;
    char buf[BSZ];

    memset(buf, 'a', BSZ - 2);
    buf[BSZ - 2] = '\0';
    buf[BSZ - 1] = 'X';
    if ((fp = fmemopen(buf, BSZ, "w+")) == NULL)
        err_sys("fmemopen failed");
    printf("initial buffer contents: %s\n", buf);
    fprintf(fp, "hello word");
    printf("before flush: %s\n", buf);
    fflush(fp);
    printf("after fflush: %s\n", buf);
    printf("len of string in buf = %ld\n", (long) strlen(buf));

    memset(buf, 'b', BSZ - 2);
    buf[BSZ - 2] = '\0';
    buf[BSZ - 1] = 'X';
    if ((fp = fmemopen(buf, BSZ, "w+")) == NULL)
        err_sys("fmemopen failed");
    printf("initial buffer contents: %s\n", buf);
    fprintf(fp, "hello word");
    fseek(fp, 0, SEEK_SET);
    printf("after fseek: %s\n", buf);
    printf("len of string in buf = %ld\n", (long) strlen(buf));

    memset(buf, 'c', BSZ - 2);
    buf[BSZ - 2] = '\0';
    buf[BSZ - 1] = 'X';
    if ((fp = fmemopen(buf, BSZ, "w+")) == NULL)
        err_sys("fmemopen failed");
    printf("initial buffer contents: %s\n", buf);
    fprintf(fp, "hello word");
    fclose(fp);
    printf("after fclose: %s\n", buf);
    printf("len of string in buf = %ld\n", (long) strlen(buf));
}