如何知道“ errno”是什么意思？

打电话execl(...)时我得到一个errno=2。这是什么意思？我怎么知道这个意思errno？

您可以strerror()用来获取易于理解的错误号字符串。这是由相同的字符串打印出来的，perror()但是如果您要格式化错误消息而不是标准错误输出，这将很有用。

例如：

#include <errno.h>
#include <string.h>

/* ... */

if(read(fd, buf, 1)==-1) {
    printf("Oh dear, something went wrong with read()! %s\n", strerror(errno));
}

Linux还支持显式线程安全变体strerror_r()。

perror您可以errno使用以下单行代码在系统上检索值的完整列表，而不必在得到的任何错误代码上运行：

cpp -dM /usr/include/errno.h | grep 'define E' | sort -n -k 3

在Linux上，还有一个非常简洁的工具，可以立即告诉每个错误代码意味着什么。在Ubuntu上：apt-get install errno。

然后，例如，如果您想获取错误类型2的描述，只需errno 2在终端中输入。

与errno -l您一起获得所有错误及其说明的列表。与以前的张贴者提到的其他方法相比，要容易得多。

这是errno -l为便于阅读而重新格式化的输出：

  1   EPERM             Operation not permitted
  2   ENOENT            No such file or directory
  3   ESRCH             No such process
  4   EINTR             Interrupted system call
  5   EIO               Input/output error
  6   ENXIO             No such device or address
  7   E2BIG             Argument list too long
  8   ENOEXEC           Exec format error
  9   EBADF             Bad file descriptor
 10   ECHILD            No child processes
 11   EAGAIN            Resource temporarily unavailable
 11   EWOULDBLOCK       Resource temporarily unavailable
 12   ENOMEM            Cannot allocate memory
 13   EACCES            Permission denied
 14   EFAULT            Bad address
 15   ENOTBLK           Block device required
 16   EBUSY             Device or resource busy
 17   EEXIST            File exists
 18   EXDEV             Invalid cross-device link
 19   ENODEV            No such device
 20   ENOTDIR           Not a directory
 21   EISDIR            Is a directory
 22   EINVAL            Invalid argument
 23   ENFILE            Too many open files in system
 24   EMFILE            Too many open files
 25   ENOTTY            Inappropriate ioctl for device
 26   ETXTBSY           Text file busy
 27   EFBIG             File too large
 28   ENOSPC            No space left on device
 29   ESPIPE            Illegal seek
 30   EROFS             Read-only file system
 31   EMLINK            Too many links
 32   EPIPE             Broken pipe
 33   EDOM              Numerical argument out of domain
 34   ERANGE            Numerical result out of range
 35   EDEADLK           Resource deadlock avoided
 35   EDEADLOCK         Resource deadlock avoided
 36   ENAMETOOLONG      File name too long
 37   ENOLCK            No locks available
 38   ENOSYS            Function not implemented
 39   ENOTEMPTY         Directory not empty
 40   ELOOP             Too many levels of symbolic links
 42   ENOMSG            No message of desired type
 43   EIDRM             Identifier removed
 44   ECHRNG            Channel number out of range
 45   EL2NSYNC          Level 2 not synchronized
 46   EL3HLT            Level 3 halted
 47   EL3RST            Level 3 reset
 48   ELNRNG            Link number out of range
 49   EUNATCH           Protocol driver not attached
 50   ENOCSI            No CSI structure available
 51   EL2HLT            Level 2 halted
 52   EBADE             Invalid exchange
 53   EBADR             Invalid request descriptor
 54   EXFULL            Exchange full
 55   ENOANO            No anode
 56   EBADRQC           Invalid request code
 57   EBADSLT           Invalid slot
 59   EBFONT            Bad font file format
 60   ENOSTR            Device not a stream
 61   ENODATA           No data available
 62   ETIME             Timer expired
 63   ENOSR             Out of streams resources
 64   ENONET            Machine is not on the network
 65   ENOPKG            Package not installed
 66   EREMOTE           Object is remote
 67   ENOLINK           Link has been severed
 68   EADV              Advertise error
 69   ESRMNT            Srmount error
 70   ECOMM             Communication error on send
 71   EPROTO            Protocol error
 72   EMULTIHOP         Multihop attempted
 73   EDOTDOT           RFS specific error
 74   EBADMSG           Bad message
 75   EOVERFLOW         Value too large for defined data type
 76   ENOTUNIQ          Name not unique on network
 77   EBADFD            File descriptor in bad state
 78   EREMCHG           Remote address changed
 79   ELIBACC           Can not access a needed shared library
 80   ELIBBAD           Accessing a corrupted shared library
 81   ELIBSCN           .lib section in a.out corrupted
 82   ELIBMAX           Attempting to link in too many shared libraries
 83   ELIBEXEC          Cannot exec a shared library directly
 84   EILSEQ            Invalid or incomplete multibyte or wide character
 85   ERESTART          Interrupted system call should be restarted
 86   ESTRPIPE          Streams pipe error
 87   EUSERS            Too many users
 88   ENOTSOCK          Socket operation on non-socket
 89   EDESTADDRREQ      Destination address required
 90   EMSGSIZE          Message too long
 91   EPROTOTYPE        Protocol wrong type for socket
 92   ENOPROTOOPT       Protocol not available
 93   EPROTONOSUPPORT   Protocol not supported
 94   ESOCKTNOSUPPORT   Socket type not supported
 95   ENOTSUP           Operation not supported
 95   EOPNOTSUPP        Operation not supported
 96   EPFNOSUPPORT      Protocol family not supported
 97   EAFNOSUPPORT      Address family not supported by protocol
 98   EADDRINUSE        Address already in use
 99   EADDRNOTAVAIL     Cannot assign requested address
100   ENETDOWN          Network is down
101   ENETUNREACH       Network is unreachable
102   ENETRESET         Network dropped connection on reset
103   ECONNABORTED      Software caused connection abort
104   ECONNRESET        Connection reset by peer
105   ENOBUFS           No buffer space available
106   EISCONN           Transport endpoint is already connected
107   ENOTCONN          Transport endpoint is not connected
108   ESHUTDOWN         Cannot send after transport endpoint shutdown
109   ETOOMANYREFS      Too many references: cannot splice
110   ETIMEDOUT         Connection timed out
111   ECONNREFUSED      Connection refused
112   EHOSTDOWN         Host is down
113   EHOSTUNREACH      No route to host
114   EALREADY          Operation already in progress
115   EINPROGRESS       Operation now in progress
116   ESTALE            Stale file handle
117   EUCLEAN           Structure needs cleaning
118   ENOTNAM           Not a XENIX named type file
119   ENAVAIL           No XENIX semaphores available
120   EISNAM            Is a named type file
121   EREMOTEIO         Remote I/O error
122   EDQUOT            Disk quota exceeded
123   ENOMEDIUM         No medium found
124   EMEDIUMTYPE       Wrong medium type
125   ECANCELED         Operation canceled
126   ENOKEY            Required key not available
127   EKEYEXPIRED       Key has expired
128   EKEYREVOKED       Key has been revoked
129   EKEYREJECTED      Key was rejected by service
130   EOWNERDEAD        Owner died
131   ENOTRECOVERABLE   State not recoverable
132   ERFKILL           Operation not possible due to RF-kill
133   EHWPOISON         Memory page has hardware error

我在Vim中使用表格格式来对齐列：

:%Tab /^[^ ]*\zs /r1l1l1
:%Tab /^ *[^ ]* *[^ ]*\zs /l1

错误代码2表示“找不到文件/目录”。通常，您可以使用perror函数来打印人类可读的字符串。

有一些有用的函数可以处理errno。（为了清楚起见，它们是内置的libc-我只是提供示例实现，因为有些人发现阅读代码比阅读英语更清晰。）

#include <string.h>
char *strerror(int errnum);

/* you can think of it as being implemented like this: */
static char strerror_buf[1024];
const char *sys_errlist[] = {
    [EPERM]  = "Operation not permitted",
    [ENOENT] = "No such file or directory",
    [ESRCH]  = "No such process",
    [EINTR]  = "Interrupted system call",
    [EIO]    = "I/O error",
    [ENXIO]  = "No such device or address",
    [E2BIG]  = "Argument list too long",
    /* etc. */
};
int sys_nerr = sizeof(sys_errlist) / sizeof(char *);
char *strerror(int errnum) {
    if (0 <= errnum && errnum < sys_nerr && sys_errlist[errnum])
        strcpy(strerror_buf, sys_errlist[errnum]);
    else
        sprintf(strerror_buf, "Unknown error %d", errnum);
    return strerror_buf;
}

strerror返回描述您传递给它的错误号的字符串。注意，这不是线程安全或中断安全的；可以免费重写字符串并在下一次调用时返回相同的指针。使用strerror_r如果需要有关的忧虑。

#include <stdio.h>
void perror(const char *s);

/* you can think of it as being implemented like this: */
void perror(const char *s) {
    fprintf(stderr, "%s: %s\n", s, strerror(errno));
}

perror打印出您给它的消息，外加描述当前errno为标准错误的字符串。

这比在中查找代码要快errno.h，比在此发布的大多数解决方案要短，并且不需要安装第三方工具：

perl -E 'say $!=shift' 2

产量

No such file or directory

#include <errno.h> 
#include <stdio.h> 
#include <stdlib.h> 

int main(int i, char *c[]) { 
  if (i != 2)  
    fprintf(stderr, "Usage: perror errno\n"); 
  else { 
    errno = atoi(c[1]); 
    perror(""); 
  } 
  exit(0); 
}    

在Solaris上工作。
cc perror.c -o perror<<使用此行进行编译

这是文档。那应该告诉您这意味着什么以及如何处理它们。您应该避免使用数字值，也不要使用此处列出的常数，因为数字在不同系统之间可能会发生变化。

我使用以下脚本：

#!/usr/bin/python

import errno
import os
import sys

toname = dict((str(getattr(errno, x)), x) 
              for x in dir(errno) 
              if x.startswith("E"))
tocode = dict((x, getattr(errno, x)) 
              for x in dir(errno) 
              if x.startswith("E"))

for arg in sys.argv[1:]:
    if arg in tocode:
        print arg, tocode[arg], os.strerror(tocode[arg])
    elif arg in toname:
        print toname[arg], arg, os.strerror(int(arg))
    else:
        print "Unknown:", arg

键入sudo apt-get install moreutils，然后在安装后键入errno 2。您还可以errno -l将所有错误号用于，也可以通过将其错误传递到来仅查看文件错误号grep，如下所示：errno | grep file。

呼叫

perror("execl");

如果发生错误。

样品：

if(read(fd, buf, 1)==-1) {
    perror("read");
}

和的手册页errno(3)也perror(3)很有趣...

当您使用strace（在Linux上）运行二进制文件时，它将输出系统调用的返回结果以及错误号的含义。有时这可能对您有用。

我在我的.bashrc文件如下功能-它查找从头文件errno值（可以是/usr/include/errno.h，/usr/include/linux/errno.h等等等等）

如果在计算机上安装了头文件，它将起作用；-)

通常头文件有错误+接下来是注释中的说明；以下内容：

./asm-generic/errno-base.h:#define EAGAIN 11 / *再试一次* /

function errno()
{
    local arg=$1

    if [[ "x$arg" == "x-h" ]]; then
        cat <<EOF
        Usage: errno <num>
        Prints text that describes errno error number
        EOF
    else
        pushd /usr/include
        find . -name "errno*.h" | xargs grep   "[[:space:]]${arg}[[:space:]]"
        popd
    fi
}

它的意思是：

找不到文件或目录。