致电execl(...)时，我会收到errno=2。这是什么意思？我怎么知道这个errno的含义？
答案 0 :(得分：308)
您可以使用strerror()获取错误编号的人类可读字符串。这是由perror()打印的相同字符串，但如果您将错误消息格式化为标准错误输出以外的其他内容，则此字符串很有用。
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explicit-threadsafe变体strerror_r()。
答案 1 :(得分：52)
您可以使用以下单行检索系统上的perror值的完整列表，而不是对您获得的任何错误代码运行errno：
cpp -dM /usr/include/errno.h | grep 'define E' | sort -n -k 3
答案 2 :(得分：41)
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的含义。在Ubuntu上：apt-get install errno。
然后，如果您想获得错误类型2的描述，只需在终端中输入errno 2。
使用errno -l，您会看到包含所有错误及其说明的列表。以前的海报提到的其他方法要容易得多。
答案 3 :(得分：23)
以下是errno -l为了可读性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中使用了tabularise来对齐列：
:%Tab /^[^ ]*\zs /r1l1l1
:%Tab /^ *[^ ]* *[^ ]*\zs /l1
答案 4 :(得分：20)
错误代码2表示“找不到文件/目录”。通常，您可以使用perror函数打印人类可读的字符串。
答案 5 :(得分：7)
有一些用于处理errno的有用功能。 （只是为了说清楚，这些内置于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返回一个字符串，描述您传递给它的错误号。注意，这不是线程或中断安全的;可以自由地重写字符串并在下次调用时返回相同的指针。如果您需要担心，请使用strerror_r。
#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将您提供的消息以及描述当前errno的字符串打印出标准错误。
答案 6 :(得分：6)
这比查找errno.h中的代码更快，比此处发布的大多数解决方案更短，并且不需要安装第三方工具：
perl -E 'say $!=shift' 2
产量
No such file or directory
答案 7 :(得分：5)
这是the documentation。这应该告诉你它意味着什么以及如何处理它们。您应该避免使用数值并使用其中列出的常量，因为数字可能会在不同系统之间发生变化。
答案 8 :(得分：5)
#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);
}
适用于Solaris
cc perror.c -o perror＆lt;＆lt;用这一行编译它
答案 9 :(得分：3)
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
答案 10 :(得分：2)
呼叫
perror("execl");
如果有错误。
样品：
if(read(fd, buf, 1)==-1) {
perror("read");
}
errno(3)和perror(3)的联机帮助页也很有趣......
答案 11 :(得分：1)
键入sudo apt-get install moreutils，然后在安装完成后，键入errno 2。您还可以使用errno -l来表示所有错误编号，或者只使用grep来查看文件错误编号，如下所示：errno | grep file。
答案 12 :(得分：0)
这意味着：
找不到文件或目录。
答案 13 :(得分：0)
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值以及错误号的含义。这有时对你有用。
答案 14 :(得分：0)
我的.bashrc文件中有以下函数 - 它从头文件中查找errno值（可以是/usr/include/errno.h，/usr/include/linux/errno.h等等。）
如果机器上安装了头文件，它会起作用; - ）
通常头文件有错误+接下来是注释中的解释;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
}