C getline() 在 EOF 之前返回 -1答案

【问题标题】：C getline() returns -1 before EOFC getline() 在 EOF 之前返回 -1
【发布时间】：2016-02-18 09:11:50
【问题描述】：

我在 c 程序中使用 getline() 函数从文件中读取行，将读取信息放入结构中，以该结构作为参数创建线程，然后重复。但是，它 getline() 在 EOF 之前返回 -1，在提供的文件中“id: test2”下的第二组参数之后。
由于 gdb 中的 print errno 返回 0，我认为没有错误，并且 getline() 似乎以某种方式相信它已达到 EOF。
创建线程部分已被注释掉，因为它与手头的问题无关。

代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>
#include <sys/time.h>

#define BUFFER_SIZE 256

time_t cur;
char* keypath = "home/chy/.ssh/id_rsa";
int logfreq = 1;
int hashfreq = 180;

struct getArgs
{
  const char* id;
  const char* hostaddr;
  uint16_t port;
  const char* uname;
  const char* path;
};

int main(int argc, char **argv)
{
  int th_max = 5;
  int th_count = 0;
  pthread_t* ths = (pthread_t*) malloc(th_max * sizeof(pthread_t));

  FILE* fp;
  fp = fopen("config.txt", "r");

  char* line = NULL;
  char buf[128];
  int r = 0;
  size_t len = 0;
  ssize_t read;

  system("mkdir logs && chmod -R a+r logs");

  while(1)
  {
    pthread_t th;
//Get ID
    while((read = getline(&line, &l, fp)) != -1)
    {
      if(!(read > 0))
        continue;
      if(sscanf(line, "id: %[^\n]\n", buf) == 1)
        break;
      if(sscanf(line, "keypath: %[^\n]\n", buf) == 1)
        keypath = strdup(buf);
      else if(sscanf(line, "logfreq: %d\n", &r) == 1)
        logfreq = r;
      else if(sscanf(line, "hashfreq: %d\n", &r) == 1)
        hashfreq = r;
    }
    if(read == -1)
      break;
    struct getArgs* args = (struct getArgs*)malloc(sizeof(struct getArgs));
    args->id = strdup(buf);
//Get Host Address
    if(getline(&line, &len, fp) == -1)
    {
      free_args(args);
      break;
    }
    if(sscanf(line, "hostaddr: %[^\n]\n", buf) != 1)
    {
      free_args(args);
      continue;
    }
    args->hostaddr = strdup(buf);
//Get Port Number
    if(getline(&line, &len, fp) == -1)
    {
      free_args(args);
      break;
    }
    if(sscanf(line, "port: %d\n", &r) != 1)
    {
      free_args(args);
      continue;
    }
    args->port = r;
//Get Username
    if(getline(&line, &len, fp) == -1)
    {
      free_args(args);
      break;
    }
    if(sscanf(line, "username: %[^\n]\n", buf) != 1)
    {
      free_args(args);
      continue;
    }
args->uname = strdup(buf);
//def Path
    if(getline(&line, &len, fp) == -1)
    {
      free_args(args);
      break;
    }
    if(sscanf(line, "path: %[^\n]\n", buf) != 1)
    {
      free_args(args);
      continue;
    }
    args->path = strdup(buf);

//    int err = pthread_create(&th, NULL, &getFiles, args);

    if(th_count > th_max)
    {
      th_max *= 2;
      ths = (pthread_t*)realloc(ths, th_max * sizeof(pthread_t));
    }
    *(ths+th_count * sizeof(pthread_t)) = th;
    th_count++;
  }

  fclose(fp);

  while(1);
}

文件：

keypath: /home/username/.ssh/id_rsaNOPASSWORD
id: test1
hostaddr: XXX.XXX.XXX.XXX
port: 22
username: hpc
path: /home/hpc/
id: test2
hostaddr: XXX.XXX.XXX.XXX
port: 22
username: hpc
path: /home/hpc/
id: test3
hostaddr: XXX.XXX.XXX.XXX
port: 22
username: hpc
path: /home/hpc/
id: test4
hostaddr: XXX.XXX.XXX.XXX
port: 3844
username: uname
path: /home/uname/hpc/

最后一个getline()之前文件指针的内容：

{_flags = -72539000,
  _IO_read_ptr = 0x7ffff7ff80d0 "    \nid: test3\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test4\nhostaddr: XXX.XXX.XXX.XXX\nport: 3844\nusername: uname\npath: /home/uname/hpc/\n\n",
  _IO_read_end = 0x401d10 "H\211l$\330L\211d$\340H\215-\277\006 ",
  _IO_read_base = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_write_base = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_write_ptr = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_write_end = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_buf_base = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"..., _IO_buf_end = 0x7ffff7ff9000 "P\220\377\367\377\177", _IO_save_base = 0x0, _IO_backup_base = 0x0, _IO_save_end = 0x0, _markers = 0x0, _chain = 0x7ffff7bbb880, _fileno = 7, _flags2 = 0, _old_offset = 0, _cur_column = 0,
  _vtable_offset = 0 '\000', _shortbuf = "", _lock = 0x603120, _offset = -1, __pad1 = 0x0, __pad2 = 0x603130, __pad3 = 0x0, __pad4 = 0x0, __pad5 = 0, _mode = -1, _unused2 = '\000' <repeats 19 times>}

之后：

{_flags = -72538984,
  _IO_read_ptr = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_read_end = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_read_base = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_write_base = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_write_ptr = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_write_end = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"...,
  _IO_buf_base = 0x7ffff7ff8000 "keypath: /home/username/.ssh/id_rsaNOPASSWORD\n    \nid: test1\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /home/hpc/\n    \nid: test2\nhostaddr: XXX.XXX.XXX.XXX\nport: 22\nusername: hpc\npath: /ho"..., _IO_buf_end = 0x7ffff7ff9000 "P\220\377\367\377\177", _IO_save_base = 0x0, _IO_backup_base = 0x0, _IO_save_end = 0x0, _markers = 0x0, _chain = 0x7ffff7bbb880, _fileno = 7, _flags2 = 0, _old_offset = 0, _cur_column = 0,
  _vtable_offset = 0 '\000', _shortbuf = "", _lock = 0x603120, _offset = -1, __pad1 = 0x0, __pad2 = 0x603130, __pad3 = 0x0, __pad4 = 0x0, __pad5 = 0, _mode = -1, _unused2 = '\000' <repeats 19 times>}

我也尝试使用 fgets() 而不是 getline() 来实现相同的功能，但结果相同。
什么可能导致此问题？

编辑：
我已经在同一个文件上运行了代码，除了没有多余的空格/空白行以及切换顺序以查看是否有任何影响，但结果是相同的。
我还可以确认 test1 和 test2 的结构已正确填充。

{id = 0x6032e0 "test1", hostaddr = 0x603300 "XXX.XXX.XXX.XXX", port = 22, uname = 0x603320 "hpc", path = 0x603340 "/home/hpc/"}
{id = 0x603390 "test2", hostaddr = 0x6033b0 "XXX.XXX.XXX.XXX", port = 22, uname = 0x6033d0 "hpc", path = 0x6033f0 "/home/hpc/"}

编辑：代码和文件的版本更改

【问题讨论】：

其余的变量在哪里声明？ keypath、logfreq 等。是全局变量吗？
是的，为了清楚起见，我已经编辑了它们。
您是否在启用 Warnings 的情况下进行编译？（即在你的编译字符串中有-Wall -Wextra？）我问的原因是你在你的sscanf字符串中签名/取消了type不匹配）。您对EOF 的问题很可能来自sscanf，例如如果在第一次成功转换或匹配失败发生之前到达输入末尾，则返回EOF。要确认，请将getline 和sscanf 放在不同if 测试中的不同行以隔离。
我已将代码编辑为用于测试您的建议的版本。刚刚尝试使用 Wall 和 Wextra，相关警告都与将 int* 传递给 uint32_t* 有关。我修复了这些并再次运行程序，但结果保持不变。
"The file:" 是您使用的完整数据文件吗？今晚晚些时候我将有一点时间来全面调试代码，但在此之前，我想确保我有当前的输入。

标签： c eof getline

【解决方案1】：

线

sscanf(line, "id: %[^\n]\n", buf) != 1

不会匹配空行，导致您的读取循环在该点不同步。随着 id: test2 被吞噬，进一步的问题从那里接踵而至，最终你遇到了 EOF。

[      Matches a nonempty sequence of characters ...

【讨论】：

谢谢，但我尝试在没有过多空格/换行符的配置文件上运行相同的代码，结果是相同的。我会在上面的帖子中澄清这一点。
没有过多的空格/换行符是什么意思？只需要1 blank line（或连续两个newlines），问题就出现了。您可能需要在调用sscanf 之前将sscanf 移入读取循环并测试if (read > 0)。
@DavidC.Rankin 没有多余的换行符，我的意思是没有双换行符的实例。只是为了确保，我按照你的建议做了，结果是一样的。

【解决方案2】：

除了 cmets 中讨论的 unsigned/signed type 不匹配之外，您遇到的主要问题是测试中使用的冲突逻辑，以及对 @987654322 的多次组织松散的调用@ 和 sscanf 您将在其中测试 if ((read = getline ... || sscanf ...)，其中 getline 或 sscanf（在输入或匹配失败时）可能会返回 EOF (-1)，但无法说出问题所在。要清理逻辑，您需要读取配置文件，您 (1) 读取该行 - 一次，(2) 解析标签和值，然后 ( 3) 测试tag 和value 并采取必要的措施。

坚持这种方法，并忽略与您的读取问题无关的线程代码，我调试/重新编写了您的输入例程，为您提供了一种以理智的方式处理读取和分离的方法的示例。在这样做的过程中，我将所有设置收集在一个指向结构的指针数组中（例如struct getArgs **args;）。您可能不需要使用您的 pthread 方案将每个结构收集到一个结构数组中，但出于示例目的，已进行了更改。

我还在下面提供了第二个示例，该示例显示了一种额外的方法，该方法进行了更多检查，以确保在 id、hostaddr、端口、用户名和路径组中读取您的值。第一个简单示例将处理在输入文件中跳过空行：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#define NARGS  32
#define TSIZE  16
#define VSIZE 256

char *keypath = "home/chy/.ssh/id_rsa";
int logfreq = 1;
int hashfreq = 180;

struct getArgs {
    const char *id;
    const char *hostaddr;
    uint16_t port;
    const char *uname;
    const char *path;
};

void *xcalloc (size_t n, size_t s);
void *xrealloc_dp (void *ptr, size_t *n);

int main (int argc, char **argv)
{
    struct getArgs **args = NULL;
    char *line = NULL;
    size_t len = 0;
    size_t idx = 0;
    size_t nargs = NARGS;
    size_t i;
    ssize_t read;
    FILE *fp = argc > 1 ? fopen (argv[1], "r") : fopen ("config.txt", "r");

    if (!fp) { fprintf (stderr, "file open failed.\n"); return 1; }

    /* allocate NARGS pointer to struct getArgs */
    args = xcalloc (NARGS, sizeof *args);

    /* read each line in file */
    while ((read = getline (&line, &len, fp)) != -1) {

        if (read == 1) continue;    /* skip blank lines */

        char tag[TSIZE] = {0};
        char val[VSIZE] = {0};

        /* separate tag and value (val) */
        if (sscanf (line, "%s %[^\n]%*c", tag, val) != 2) {
            fprintf (stderr, "error: sscanf conversion failed.\n");
            break;
        }

        /* handle keypath, logfreq, hashfreq */
        if (strcmp (tag, "keypath:") == 0) {
            keypath = strdup (val);
            continue;
        }

        if (strcmp (tag, "logfreq:") == 0) {
            logfreq = (int)strtol (val, NULL, 10);
            continue;
        }

        if (strcmp (tag, "hashfreq:") == 0) {
            hashfreq = (int)strtol (val, NULL, 10);
            continue;
        }

        /* allocate space for args[idx] if "id:", then
        handle id, hostaddr, port, username, path */
        if (strcmp (tag, "id:") == 0) {
            args[idx] = calloc (1, sizeof **args);
            args[idx]->id = strdup (val);
            continue;
        }

        if (strcmp (tag, "hostaddr:") == 0) {
            args[idx]->hostaddr = strdup (val);
            continue;
        }

        if (strcmp (tag, "port:") == 0) {
            args[idx]->port = (uint16_t)strtoul (val, NULL, 10);
            continue;
        }

        if (strcmp (tag, "username:") == 0) {
            args[idx]->uname = strdup (val);
            continue;
        }

        /* increment idx on path */
        if (strcmp (tag, "path:") == 0)
            args[idx++]->path = strdup (val);

        if (idx == nargs) /* check idx, realloc */
            args = xrealloc_dp (args, &nargs);
    }
    fclose (fp);

    printf ("\n keypath  : %s\n logfreq  : %d\n hashfreq : %d\n",
            keypath, logfreq, hashfreq);

    for (i = 0; i < idx; i++)
        printf ("\n id       : %s\n hostaddr : %s\n port     : %hu\n"
                " username : %s\n path     : %s\n", args[i]->id, args[i]->hostaddr,
                args[i]->port, args[i]->uname, args[i]->path);

    for (i = 0; i < idx; i++)
        free (args[i]);
    free (args);

    return 0;
}

/* calloc with error check, exit on failure */
void *xcalloc (size_t n, size_t s)
{
    register void *memptr = calloc (n, s);
    if (memptr == 0) {
        fprintf (stderr, "xcalloc() error: virtual memory exhausted.\n");
        exit (EXIT_FAILURE);
    }

    return memptr;
}

/* reallocate memory for a double-pointer from 'n' to 2 * 'n'
 * returns pointer to reallocated block on success, exit on
 * failure
 */
void *xrealloc_dp (void *ptr, size_t *n)
{
    void **p = ptr;
    void *tmp = realloc (p, 2 * *n * sizeof tmp);
    if (!tmp) {
        fprintf (stderr, "xrealloc_dp() error: virtual memory exhausted.\n");
        exit (EXIT_FAILURE);
    }
    p = tmp;
    memset (p + *n, 0, *n * sizeof tmp); /* set new pointers NULL */
    *n *= 2;

    return p;
}

xcalloc 和xrealloc_dp 函数只是对calloc 和realloc（用于双指针）进行错误检查以保持代码主体和逻辑清晰的函数。我在以下测试输入上运行代码并收到以下输出：

输入测试文件（带空行）

$ cat ../dat/idhostaddrport.txt
keypath: /home/username/.ssh/id_rsaNOPASSWORD
logfreq: 2
hashfreq: 250

id: test1
hostaddr: XXX.XXX.XXX.XXX
port: 221
username: hpc1
path: /home/hpc1/

id: test2
hostaddr: XXX.XXX.XXX.XXX
port: 222
username: hpc2
path: /home/hpc2/

id: test3
hostaddr: XXX.XXX.XXX.XXX
port: 223
username: hpc3
path: /home/hpc3/

id: test4
hostaddr: XXX.XXX.XXX.XXX
port: 3844
username: uname
path: /home/uname/hpc/

输出

$ ./bin/getline_sscanf_dbg ../dat/idhostaddrport.txt

 keypath  : /home/username/.ssh/id_rsaNOPASSWORD
 logfreq  : 2
 hashfreq : 250

 id       : test1
 hostaddr : XXX.XXX.XXX.XXX
 port     : 221
 username : hpc1
 path     : /home/hpc1/

 id       : test2
 hostaddr : XXX.XXX.XXX.XXX
 port     : 222
 username : hpc2
 path     : /home/hpc2/

 id       : test3
 hostaddr : XXX.XXX.XXX.XXX
 port     : 223
 username : hpc3
 path     : /home/hpc3/

 id       : test4
 hostaddr : XXX.XXX.XXX.XXX
 port     : 3844
 username : uname

您应该努力的一件事是进一步验证您的输入的方法。确保如果您读取id，您也会读取每个id 的剩余值hostaddr 到path。添加最少检查的一种简单变化是对读取循环的以下更改：

    /* read each line in file */
    while ((read = getline (&line, &len, fp)) != -1) {

        if (read == 1) continue;    /* skip blank lines */

        char tag[TSIZE] = {0};
        char val[VSIZE] = {0};

        /* separate tag and value (val) */
        if (sscanf (line, "%s %[^\n]%*c", tag, val) != 2) {
            fprintf (stderr, "error: sscanf conversion failed.\n");
            break;
        }

        /* handle keypath, logfreq, hashfreq */
        if (strcmp (tag, "keypath:") == 0) {
            keypath = strdup (val);
            continue;
        }

        if (strcmp (tag, "logfreq:") == 0) {
            logfreq = (int)strtol (val, NULL, 10);
            continue;
        }

        if (strcmp (tag, "hashfreq:") == 0) {
            hashfreq = (int)strtol (val, NULL, 10);
            continue;
        }

        /* allocate space for args[idx] if "id:", then
        handle id, hostaddr, port, username, path */
        if (strcmp (tag, "id:") == 0) {

            args[idx] = calloc (1, sizeof **args);
            args[idx]->id = strdup (val);
            size_t tagseq = 0;

            while ((read = getline (&line, &len, fp)) != -1) {

                if (read == 1) continue;    /* skip blank lines */

                /* separate tag and value (val) */
                if (sscanf (line, "%s %[^\n]%*c", tag, val) != 2) {
                    fprintf (stderr, "error: sscanf conversion failed.\n");
                    break;
                }

                if (strcmp (tag, "hostaddr:") == 0) {
                    if (tagseq != 0) { 
                        fprintf (stderr, "error: tagseq failed for hostaddr.\n");
                        exit (EXIT_FAILURE);
                    }
                    args[idx]->hostaddr = strdup (val);
                    tagseq++;
                    continue;
                }

                if (strcmp (tag, "port:") == 0) {
                    if (tagseq != 1) { 
                        fprintf (stderr, "error: tagseq failed for port.\n");
                        exit (EXIT_FAILURE);
                    }
                    args[idx]->port = (uint16_t)strtoul (val, NULL, 10);
                    tagseq++;
                    continue;
                }

                if (strcmp (tag, "username:") == 0) {
                    if (tagseq != 2) { 
                        fprintf (stderr, "error: tagseq failed for username.\n");
                        exit (EXIT_FAILURE);
                    }
                    args[idx]->uname = strdup (val);
                    tagseq++;
                    continue;
                }

                /* increment idx on path */
                if (strcmp (tag, "path:") == 0) {
                    if (tagseq != 3) { 
                        fprintf (stderr, "error: tagseq failed for path.\n");
                        exit (EXIT_FAILURE);
                    }
                    args[idx++]->path = strdup (val);
                    break;
                }
            }
        }

        if (idx == nargs) /* check idx, realloc */
            args = xrealloc_dp (args, &nargs);
    }
    fclose (fp);

看看两者，如果您有任何其他问题，请告诉我。

【讨论】：