题
当调用execl(...)
,我得到一个errno=2
。这是什么意思?我怎么能知道这个errno
的含义是什么?
解决方案
您可以使用 strerror()
以得到一个人类可读的字符串错误编号。这是相同的字符串印刷由 perror()
但它是有用的,如果你格式化比标准错误输出以外的内容的错误信息。
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还支持显式线程变体strerror_r()
。
其他提示
而不是任何错误代码,就可以看到运行perror
的,你可以在系统上检索errno
值的完整列表,与下面的一行代码:
cpp -dM /usr/include/errno.h | grep 'define E' | sort -n -k 3
在Linux上也有一个非常整洁的工具,它可以告诉马上了每个错误代码的含义。在Ubuntu:apt-get install errno
然后,如果例如要获取错误类型2的说明中,只是在终端上键入errno 2
。
使用errno -l
你得到所有的错误及其说明的列表。容易得多,通过以前提到的海报的其它方法。
下面是从errno -l
输出重新格式化为可读性:
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
我用tabularise Vim中对齐的列:
:%Tab /^[^ ]*\zs /r1l1l1
:%Tab /^ *[^ ]* *[^ ]*\zs /l1
错误代码2的意思是“未找到文件/目录”。一般情况下,你可以使用 PERROR 功能打印人类可读的字符串。
有一些有用的功能,用于处理errno
s。 (只是要清楚,这些都是内置在libc
- 我只是提供示例实现,因为有些人觉得读码比读英语更清晰)
#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
返回描述你传递给它的错误号的字符串。注意,这不是thread-或中断安全;它是免费的改写串,并在下次调用返回相同的指针。如果你需要担心的是使用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
打印出你给它的消息时,加描述当前errno
的字符串,向标准错误。
这是不是找起来errno.h
的代码快,短贴在这里大部分的解决方案,它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);
}
作品在Solaris。结果
cc perror.c -o perror
<<使用此行编译它
下面是的文档。这应该告诉你这是什么意思,并与他们做什么。应该避免使用数字值,并使用列有作为常数,如数量可以不同的系统之间进行切换。
我使用下面的脚本:
#!/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
呼叫
perror("execl");
在错误的情况下。
样品:
if(read(fd, buf, 1)==-1) {
perror("read");
}
和errno(3)
perror(3)
的手册页是有趣的,太...
类型sudo apt-get install moreutils
然后一旦已经安装,类型errno 2
。您还可以使用errno -l
所有错误数字,或者通过管道它grep
,这样只能看到文件的人。errno | grep file
当您使用 strace的(在Linux上)运行的二进制文件,它将输出从系统调用和什么错误编号是指返回。这有时可能是对你有用。
我有以下功能在我的.bashrc文件 - 它查找从报头文件中的错误值
(可以是/usr/include/errno.h
,/usr/include/linux/errno.h
等,等)。
它的工作原理,如果头文件在机器上安装的; - )
一般头文件有一个错误+其次是在注释的说明;下面的一些:
./ ASM-通用/错误号-base.h:#定义EAGAIN 11 / *再次尝试* /
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
}
这意味着:
文件或目录未找到。