程序设计►操作系统►C编程

C Linux下调用sendmail命令发送邮件

用C写了一个扫描类的监控程序，为了监控的实时性，所有要发送邮件。
前提机器中必须有sendmail程序，sendmail的目录自己定义。
我测试环境的信息

[root@localhost sendmail]# uname -a
Linux localhost.localdomain 2.6.32-358.el6.i686 #1 SMP Thu Feb 21 21:50:49 UTC 2013 i686 i686 i386 GNU/Linux
[root@localhost sendmail]# cat /etc/issue
CentOS release 6.4 (Final)
Kernel r on an m

代码如下，很简单只要是思路。

#include 
#include 
#include 
//借助sendmail命令发送邮件
//邮件格式如下：
/*
*From: John Doe 
*Sender: Michael Jones 
*To: Mary Smith 
*Subject: Saying Hello
*Date: Fri, 21 Nov 1997 09:55:06 -0600
*Message-ID: <1234@local.machine.example>
*
*This is a message just to say hello.
*So, "Hello".
*/
int main(void)
{
        FILE    *fp;
        char    buffer[512];
        if( (fp=popen("/usr/sbin/sendmail -t","w")) == NULL)
        {
                perror("open /usr/sbin/sendmail errorn");
                printf("%sn", strerror(errno));
        }
        fputs("From: John Doe n", fp);
        fputs("Sender: Michael Jones n", fp);
        fputs("To: key1088 n", fp);
        fputs("Subject: Hello,wordn", fp);
        fputs("Date: Fri, 21 Nov 1997 09:55:06 -0600n", fp);
        fputs("Message-ID: <1234@local.machine.example>n", fp);
        fputs("n", fp);
        fputs("This is a message just to say hello.n", fp);
        fputs("So, Hellon", fp);
        if( pclose(fp) != 0) {
                printf("send mail error.n");
                exit(1);
        }
        printf("send mail done.n");
}
[root@localhost sendmail]# cc sendmail.c
[root@localhost sendmail]# a.out
send mail done.
[root@localhost sendmail]# tail /var/log/maillog
Mar 16 15:43:45 localhost postfix/sendmail[2124]: fatal: Recipient addresses must be specified on the command line or via the -t option
Mar 16 15:47:33 localhost postfix/qmgr[1059]: 2B7F53F87B: from=, size=431, nrcpt=1 (queue active)
Mar 16 15:47:33 localhost postfix/qmgr[1059]: 667E83F89F: from=, size=431, nrcpt=1 (queue active)
Mar 16 15:47:33 localhost postfix/smtp[2130]: 2B7F53F87B: to=, relay=none, delay=1075, delays=1075/0.08/0/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=163.com type=MX: Host not found, try again)

因为测试环境没有联网，所以是发送不成功。

程序设计►C编程

sscanf函数的用法

sscanf() - 从一个字符串中读进与指定格式相符的数据.
函数原型:
int sscanf( string str, string fmt, mixed var1, mixed var2 … );
int scanf( const char *format [,argument]… );
说明：
　　sscanf与scanf类似，都是用于输入的，只是后者以屏幕(stdin)为输入源，前者以固定字符串为输入源。
　　其中的format可以是一个或多个

程序设计►C编程

C专家编程—分析signal函数的原型声明

在ANSI标准中，signal()的声明如下：
void (*signal(int sig,void (func)(int)))(int)
signal是一个函数，它返回一个函数指针，后者所指向的函数(signal的返回值)接受一个int参数并返回void。signal函数有两个参数，一个是sig(为int类型)，另一个是func(为void()(int)类型)。
void (func)(int)是一个函数指针，所指向的函数接受一个int参数，返回值是void。
下面用typedef进行简化：
typedef void（ptr_to_func）(int);
ptr_to_func signal（int，ptr_to_func）;
网上的一个例子：

#include 
enum { RED, GREEN, BLUE };
void OutputSignal(int sig)
{
    printf("The signal you /'ve input is: ");
    switch(sig)
    {
    case RED:
        puts("RED!");
        break;
    case GREEN:
        puts("GREEN!");
        break;
    case BLUE:
        puts("BLUE!");
        break;
    }
}
void ( *signal( int sig, void (*func)(int) ) ) (int)
{
    puts("Hello, world!");
    func(sig);
    return func;
}
int main(void)
{
    (*signal(GREEN, &OutputSignal))(RED);
    return 0;
}
Output:
Hello, world!
The signal you 've input is: GREEN!
The signal you 've input is: RED!
程序设计►操作系统►Linux►C编程

POSIX basic and extended

引用：http://en.wikipedia.org/wiki/Regular_expression

POSIX basic and extended[edit]

In the POSIX standard, Basic Regular Syntax, BRE, requires that the metacharacters ( ) and { } be designated () and {}, whereas Extended Regular Syntax, ERE, does not.
Metacharacter Description
. Matches any single character (many applications exclude newlines, and exactly which characters are considered newlines is flavor-, character-encoding-, and platform-specific, but it is safe to assume that the line feed character is included). Within POSIX bracket expressions, the dot character matches a literal dot. For example, a.c matches "abc", etc., but [a.c] matches only "a", ".", or "c".
[ ] A bracket expression. Matches a single character that is contained within the brackets. For example, [abc] matches "a", "b", or "c". [a-z]specifies a range which matches any lowercase letter from "a" to "z". These forms can be mixed: [abcx-z] matches "a", "b", "c", "x", "y", or "z", as does [a-cx-z].The - character is treated as a literal character if it is the last or the first (after the ^, if present) character within the brackets: [abc-], [-abc]. Note that backslash escapes are not allowed. The ] character can be included in a bracket expression if it is the first (after the ^) character: []abc].
[^ ] Matches a single character that is not contained within the brackets. For example, [^abc] matches any character other than "a", "b", or "c".[^a-z] matches any single character that is not a lowercase letter from "a" to "z". Likewise, literal characters and ranges can be mixed.
^ Matches the starting position within the string. In line-based tools, it matches the starting position of any line.
$ Matches the ending position of the string or the position just before a string-ending newline. In line-based tools, it matches the ending position of any line.
( ) Defines a marked subexpression. The string matched within the parentheses can be recalled later (see the next entry, n). A marked subexpression is also called a block or capturing group. BRE mode requires ( ).
n Matches what the nth marked subexpression matched, where n is a digit from 1 to 9. This construct is vaguely defined in the POSIX.2 standard. Some tools allow referencing more than nine capturing groups.
* Matches the preceding element zero or more times. For example, ab*c matches "ac", "abc", "abbbc", etc. [xyz]* matches "", "x", "y", "z", "zx", "zyx", "xyzzy", and so on. (ab)* matches "", "ab", "abab", "ababab", and so on.
{m,n} Matches the preceding element at least m and not more than n times. For example, a{3,5} matches only "aaa", "aaaa", and "aaaaa". This is not found in a few older instances of regular expressions. BRE mode requires {m,n}.
Examples:
  • .at matches any three-character string ending with "at", including "hat", "cat", and "bat".
  • [hc]at matches "hat" and "cat".
  • [^b]at matches all strings matched by .at except "bat".
  • [^hc]at matches all strings matched by .at other than "hat" and "cat".
  • ^[hc]at matches "hat" and "cat", but only at the beginning of the string or line.
  • [hc]at$ matches "hat" and "cat", but only at the end of the string or line.
  • [.] matches any single character surrounded by "[" and "]" since the brackets are escaped, for example: "[a]" and "[b]".
  • s.* matches any number of characters preceded by s , for example: "saw" and "seed".

POSIX extended[edit]

The meaning of metacharacters escaped with a backslash is reversed for some characters in the POSIX Extended Regular Expression (ERE) syntax. With this syntax, a backslash causes the metacharacter to be treated as a literal character. So, for example, ( ) is now ( ) and { } is now { }. Additionally, support is removed for n backreferences and the following metacharacters are added:
Metacharacter Description
? Matches the preceding element zero or one time. For example, ab?c matches only "ac" or "abc".
+ Matches the preceding element one or more times. For example, ab+c matches "abc", "abbc", "abbbc", and so on, but not "ac".
| The choice (also known as alternation or set union) operator matches either the expression before or the expression after the operator. For example, abc|def matches "abc" or "def".
Examples:
  • [hc]+at matches "hat", "cat", "hhat", "chat", "hcat", "cchchat", and so on, but not "at".
  • [hc]?at matches "hat", "cat", and "at".
  • [hc]*at matches "hat", "cat", "hhat", "chat", "hcat", "cchchat", "at", and so on.
  • cat|dog matches "cat" or "dog".
POSIX Extended Regular Expressions can often be used with modern Unix utilities by including the command line flag -E.

Character classes[edit]

The character class is the most basic regular expression concept after a literal match. It makes one small sequence of characters match a larger set of characters. For example, [A-Z] could stand for the alphabet, and d could mean any digit. Character classes apply to both POSIX levels. When specifying a range of characters, such as [a-Z] computer's locale settings determine the contents by the numeric ordering of the character encoding. They could store digits in that sequence, or the ordering could be abc...zABC...Z, or aAbBcC...zZ. So the POSIX standard defines a character class, which will be known by the regular expression processor installed. Those definitions are in the following table:
POSIX Non-standard Perl/Tcl Vim ASCII Description
[:alnum:] [A-Za-z0-9] Alphanumeric characters
[:word:] w w [A-Za-z0-9_] Alphanumeric characters plus "_"
W W [^A-Za-z0-9_] Non-word characters
[:alpha:] a [A-Za-z] Alphabetic characters
[:blank:] s [ t] Space and tab
b < > (?<=W)(?=w)|(?<=w)(?=W) Word boundaries
[:cntrl:] [x00-x1Fx7F] Control characters
[:digit:] d d [0-9] Digits
D D [^0-9] Non-digits
[:graph:] [x21-x7E] Visible characters
[:lower:] l [a-z] Lowercase letters
[:print:] p [x20-x7E] Visible characters and the space character
[:punct:] [][!"#$%&'()*+,./:;<=>?@^_`{|}~-] Punctuation characters
[:space:] s _s [ trnvf] Whitespace characters
S [^ trnvf] Non-whitespace characters
[:upper:] u [A-Z] Uppercase letters
[:xdigit:] x [A-Fa-f0-9] Hexadecimal digits
POSIX character classes can only be used within bracket expressions. For example, [[:upper:]ab] matches the uppercase letters and lowercase "a" and "b". An additional non-POSIX class understood by some tools is [:word:], which is usually defined as [:alnum:] plus underscore. This reflects the fact that in many programming languages these are the characters that may be used in identifiers. The editor Vim further distinguishes word and word-head classes (using the notation w and h) since in many programming languages the characters that can begin an identifier are not the same as those that can occur in other positions. Note that what the POSIX regular expression standards call character classes are commonly referred to as POSIX character classes in other regular expression flavors which support them. With most other regular expression flavors, the term character class is used to describe what POSIX calls bracket expressions. C默认在*NIX下面，可以使用这些规则，最基本的POSIX语法，不需要其他的扩展库。
程序设计►操作系统►Linux►C编程

Linux-2.6.25 select系统调用源码分析

Linux 2.6.25中的select系统调用
主要有4个函数:
sys_select：处理时间参数，调用core_sys_select。
core_sys_select：处理三个fd_set参数，调用do_select。
do_select：做select/poll的工作。在合适的时机把自己挂起等待，调用sock_poll。
sock_poll：用函数指针分派到具体的协议层函数tcp_poll、udp_poll、datagram_poll。
层层分工明确，我也要多学习这种方式啊。

/*
sys_select(fs/select.c)
处理了超时值（如果有）,将struct timeval转换成了时钟周期数,调用core_sys_select,然后检查剩余时间,处理时间
*/
asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                           fd_set __user *exp, struct timeval __user *tvp)
{
    s64 timeout = -1;
    struct timeval tv;
    int ret;
    if (tvp) {/*如果有超时值*/
        if (copy_from_user(&tv, tvp, sizeof(tv)))
            return -EFAULT;
        if (tv.tv_sec < 0 || tv.tv_usec < 0)/*时间无效*/
            return -EINVAL;
        /* Cast to u64 to make GCC stop complaining */
        if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS)
            timeout = -1;	/* 无限等待*/
        else {
            timeout = DIV_ROUND_UP(tv.tv_usec, USEC_PER_SEC/HZ);
            timeout += tv.tv_sec * HZ;/*计算出超时的相对时间,单位为时钟周期数*/
        }
    }
    /*主要工作都在core_sys_select中做了*/
    ret = core_sys_select(n, inp, outp, exp, &timeout);
    if (tvp) {/*如果有超时值*/
        struct timeval rtv;
        if (current->personality & STICKY_TIMEOUTS)/*模拟bug的一个机制,不详细描述*/
            goto sticky;
        /*rtv中是剩余的时间*/
        rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));
        rtv.tv_sec = timeout;
        if (timeval_compare(&rtv, &tv) >= 0)/*如果core_sys_select超时返回,更新时间*/
            rtv = tv;
        /*拷贝更新后的时间到用户空间*/
        if (copy_to_user(tvp, &rtv, sizeof(rtv))) {
sticky:
            /*
            * If an application puts its timeval in read-only
            * memory, we don't want the Linux-specific update to
            * the timeval to cause a fault after the select has
            * completed successfully. However, because we're not
            * updating the timeval, we can't restart the system
            * call.
            */
            if (ret == -ERESTARTNOHAND)/*ERESTARTNOHAND表明,被中断的系统调用*/
                ret = -EINTR;
        }
    }
    return ret;
}
/*core_sys_select
为do_select准备好了位图,然后调用do_select,将返回的结果集,返回到用户空间
*/
static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                           fd_set __user *exp, s64 *timeout)
{
    fd_set_bits fds;
    void *bits;
    int ret, max_fds;
    unsigned int size;
    struct fdtable *fdt;
    /* Allocate small arguments on the stack to save memory and be faster */
    /*SELECT_STACK_ALLOC 定义为256*/
    long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
    ret = -EINVAL;
    if (n < 0)
        goto out_nofds;
    /* max_fds can increase, so grab it once to avoid race */
    rcu_read_lock();
    fdt = files_fdtable(current->files);/*获取当前进程的文件描述符表*/
    max_fds = fdt->max_fds;
    rcu_read_unlock();
    if (n > max_fds)/*修正用户传入的第一个参数：fd_set中文件描述符的最大值*/
        n = max_fds;
    /*
    * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
    * since we used fdset we need to allocate memory in units of
    * long-words.
    */
    /*
    如果stack_fds数组的大小不能容纳下所有的fd_set,就用kmalloc重新分配一个大数组。
    然后将位图平均分成份,并初始化fds结构
    */
    size = FDS_BYTES(n);
    bits = stack_fds;
    if (size > sizeof(stack_fds) / 6) {
        /* Not enough space in on-stack array; must use kmalloc */
        ret = -ENOMEM;
        bits = kmalloc(6 * size, GFP_KERNEL);
        if (!bits)
            goto out_nofds;
    }
    fds.in      = bits;
    fds.out     = bits +   size;
    fds.ex      = bits + 2*size;
    fds.res_in  = bits + 3*size;
    fds.res_out = bits + 4*size;
    fds.res_ex  = bits + 5*size;
    /*get_fd_set仅仅调用copy_from_user从用户空间拷贝了fd_set*/
    if ((ret = get_fd_set(n, inp, fds.in)) ||
        (ret = get_fd_set(n, outp, fds.out)) ||
        (ret = get_fd_set(n, exp, fds.ex)))
        goto out;
    zero_fd_set(n, fds.res_in);
    zero_fd_set(n, fds.res_out);
    zero_fd_set(n, fds.res_ex);
    /*
    接力棒传给了do_select
    */
    ret = do_select(n, &fds, timeout);
    if (ret < 0)
        goto out;
    /*do_select返回,是一种异常状态*/
    if (!ret) {
        /*记得上面的sys_select不？将ERESTARTNOHAND转换成了EINTR并返回。EINTR表明系统调用被中断*/
        ret = -ERESTARTNOHAND;
        if (signal_pending(current))/*当当前进程有信号要处理时,signal_pending返回真,这符合了EINTR的语义*/
            goto out;
        ret = 0;
    }
    /*把结果集,拷贝回用户空间*/
    if (set_fd_set(n, inp, fds.res_in) ||
        set_fd_set(n, outp, fds.res_out) ||
        set_fd_set(n, exp, fds.res_ex))
        ret = -EFAULT;
out:
    if (bits != stack_fds)
        kfree(bits);/*对应上面的kmalloc*/
out_nofds:
    return ret;
}
/*do_select
真正的select在此,遍历了所有的fd,调用对应的xxx_poll函数
*/
int do_select(int n, fd_set_bits *fds, s64 *timeout)
{
    struct poll_wqueues table;
    poll_table *wait;
    int retval, i;
    rcu_read_lock();
    /*根据已经打开fd的位图检查用户打开的fd, 要求对应fd必须打开, 并且返回最大的fd*/
    retval = max_select_fd(n, fds);
    rcu_read_unlock();
    if (retval < 0)
        return retval;
    n = retval;
    /*将当前进程放入自已的等待队列table, 并将该等待队列加入到该测试表wait*/
    poll_initwait(&table);
    wait = &table.pt;
    if (!*timeout)
        wait = NULL;
    retval = 0;
    for (;;) {/*死循环*/
        unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
        long __timeout;
        /*注意:可中断的睡眠状态*/
        set_current_state(TASK_INTERRUPTIBLE);
        inp = fds->in; outp = fds->out; exp = fds->ex;
        rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
        for (i = 0; i < n; ++rinp, ++routp, ++rexp) {/*遍历所有fd*/
            unsigned long in, out, ex, all_bits, bit = 1, mask, j;
            unsigned long res_in = 0, res_out = 0, res_ex = 0;
            const struct file_operations *f_op = NULL;
            struct file *file = NULL;
            in = *inp++; out = *outp++; ex = *exp++;
            all_bits = in | out | ex;
            if (all_bits == 0) {
                /*
                __NFDBITS定义为(8 * sizeof(unsigned long)),即long的位数。
                因为一个long代表了__NFDBITS位，所以跳到下一个位图i要增加__NFDBITS
                */
                i += __NFDBITS;
                continue;
            }
            for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
                int fput_needed;
                if (i >= n)
                    break;
                /*测试每一位*/
                if (!(bit & all_bits))
                    continue;
                /*得到file结构指针，并增加引用计数字段f_count*/
                file = fget_light(i, &fput_needed);
                if (file) {
                    f_op = file->f_op;
                    mask = DEFAULT_POLLMASK;
                    /*对于socket描述符,f_op->poll对应的函数是sock_poll
                    注意第三个参数是等待队列，在poll成功后会将本进程唤醒执行*/
                    if (f_op && f_op->poll)
                        mask = (*f_op->poll)(file, retval ? NULL : wait);
                    /*释放file结构指针，实际就是减小他的一个引用计数字段f_count*/
                    fput_light(file, fput_needed);
                    /*根据poll的结果设置状态,要返回select出来的fd数目，所以retval++。
                    注意：retval是in out ex三个集合的总和*/
                    if ((mask & POLLIN_SET) && (in & bit)) {
                        res_in |= bit;
                        retval++;
                    }
                    if ((mask & POLLOUT_SET) && (out & bit)) {
                        res_out |= bit;
                        retval++;
                    }
                    if ((mask & POLLEX_SET) && (ex & bit)) {
                        res_ex |= bit;
                        retval++;
                    }
                }
                /*
                注意前面的set_current_state(TASK_INTERRUPTIBLE);
                因为已经进入TASK_INTERRUPTIBLE状态,所以cond_resched回调度其他进程来运行，
                这里的目的纯粹是为了增加一个抢占点。被抢占后，由等待队列机制唤醒。
                在支持抢占式调度的内核中（定义了CONFIG_PREEMPT），cond_resched是空操作
                */
                cond_resched();
            }
            /*根据poll的结果写回到输出位图里*/
            if (res_in)
                *rinp = res_in;
            if (res_out)
                *routp = res_out;
            if (res_ex)
                *rexp = res_ex;
        }
        wait = NULL;
        if (retval || !*timeout || signal_pending(current))/*signal_pending前面说过了*/
            break;
        if(table.error) {
            retval = table.error;
            break;
        }
        if (*timeout < 0) {
            /*无限等待*/
            __timeout = MAX_SCHEDULE_TIMEOUT;
        } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT - 1)) {
            /* 时间超过MAX_SCHEDULE_TIMEOUT,即schedule_timeout允许的最大值，用一个循环来不断减少超时值*/
            __timeout = MAX_SCHEDULE_TIMEOUT - 1;
            *timeout -= __timeout;
        } else {
            /*等待一段时间*/
            __timeout = *timeout;
            *timeout = 0;
        }
        /*TASK_INTERRUPTIBLE状态下，调用schedule_timeout的进程会在收到信号后重新得到调度的机会，
        即schedule_timeout返回,并返回剩余的时钟周期数
        */
        __timeout = schedule_timeout(__timeout);
        if (*timeout >= 0)
            *timeout += __timeout;
    }
    /*设置为运行状态*/
    __set_current_state(TASK_RUNNING);
    /*清理等待队列*/
    poll_freewait(&table);
    return retval;
}
static unsigned int sock_poll(struct file *file, poll_table *wait)
{
    struct socket *sock;
    /*约定socket的file->private_data字段放着对应的socket结构指针*/
    sock = file->private_data;
    /*对应了三个协议的函数tcp_poll,udp_poll,datagram_poll，其中udp_poll几乎直接调用了datagram_poll
    累了，先休息一下，这三个函数以后分析*/
    return sock->ops->poll(file, sock, wait);
}

其他重要函数一览
static int max_select_fd(unsigned long n, fd_set_bits *fds)
返回在fd_set中已经打开的，并且小于用户指定最大值，的fd
static inline int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
从用户空间拷贝fd_set到内核
static inline void zero_fd_set(unsigned long nr, unsigned long *fdset)
把fd_set清零
static inline unsigned long __must_check set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
把fd_set拷贝回用户空间
static inline int signal_pending(struct task_struct *p)
目前进程有信号需要处理
struct file *fget_light(unsigned int fd, int *fput_needed)
由fd得到其对应的file结构指针，并增加其引用计数
static inline void fput_light(struct file *file, int fput_needed)
释放由fget_light得到的file结构指针，减少其引用计数
set_current_state
设置当前进程的状态
static inline int cond_resched(void)
判断是否有进程需要抢占当前进程，如果是将立即发生调度。就是额外增加一个抢占点。
signed long __sched schedule_timeout(signed long timeout)
当前进程睡眠timeout个jiffies
rcu_read_lock
rcu_read_unlock
Linux 2.6新加入的rcu锁。读锁的加锁、解锁函数
参考http://www.ibm.com/developerworks/cn/linux/l-rcu
poll_freewait
poll_initwait
poll_wait
…
和文件IO，poll机制有关的几个函数，参考《Linux设备驱动(第三版)》6.3
tcp_poll
udp_poll
datagram_poll
协议层的poll函数
文件出处：http://zhangyafeikimi.iteye.com/blog/248815

Oracle►数据库

PLSQL 两种循环for和while

第一种 while

declare
i number;
begin
i:=0;
while i<=100 loop
Dbms_Output.put_line('i=' || i);
i:=i+1;
end loop;
end;

第二种 for

begin
for i in 1..100 loop
Dbms_Output.put_line('i=' || i);
end loop;
commit;
end;

第三种 也可以直接使用loop( 死循环，游标中使用)

declare
i number;
begin
i:=0;
loop
Dbms_Output.put_line('i=' || i);
i:=i+1;
end loop;
commit;
end;
Oracle►数据库

用PLSQL简单实现游标

PLSQL编程简单实现游标

declare
v_userid   t_eb_user.userid%TYPE;
v_username t_eb_user.username%TYPE;
cursor emp_cursor is
 select a.userid,a.username from t_eb_user a, t_eb_tables b where a.userid=b.userid;
begin
  open emp_cursor;
LOOP
  FETCH emp_cursor INTO v_userid, v_username;
  EXIT WHEN emp_cursor%NOTFOUND;
  dbms_output.put_line(v_userid||' '||v_username);
END LOOP;
end;
程序设计►Linux►C编程

使用inotify 监控文件创建、修改

例子为：使用inotify 监控文件创建，可用于安全防护，在创建文件时，检测文件内容，以及后续的操作。
监控类型在/usr/include/sys/inotify.h头文件查看

#define IN_ACCESS        0x00000001     /* File was accessed.  */
#define IN_MODIFY        0x00000002     /* File was modified.  */
#define IN_ATTRIB        0x00000004     /* Metadata changed.  */
#define IN_CLOSE_WRITE   0x00000008     /* Writtable file was closed.  */
#define IN_CLOSE_NOWRITE 0x00000010     /* Unwrittable file closed.  */
#define IN_CLOSE         (IN_CLOSE_WRITE | IN_CLOSE_NOWRITE) /* Close.  */
#define IN_OPEN          0x00000020     /* File was opened.  */
#define IN_MOVED_FROM    0x00000040     /* File was moved from X.  */
#define IN_MOVED_TO      0x00000080     /* File was moved to Y.  */
#define IN_MOVE          (IN_MOVED_FROM | IN_MOVED_TO) /* Moves.  */
#define IN_CREATE        0x00000100     /* Subfile was created.  */
#define IN_DELETE        0x00000200     /* Subfile was deleted.  */
#define IN_DELETE_SELF   0x00000400     /* Self was deleted.  */
#define IN_MOVE_SELF     0x00000800     /* Self was moved.  */
/* Events sent by the kernel.  */
#define IN_UNMOUNT       0x00002000     /* Backing fs was unmounted.  */
#define IN_Q_OVERFLOW    0x00004000     /* Event queued overflowed.  */
#define IN_IGNORED       0x00008000     /* File was ignored.  */
/* Helper events.  */
#define IN_CLOSE         (IN_CLOSE_WRITE | IN_CLOSE_NOWRITE)    /* Close.  */
#define IN_MOVE          (IN_MOVED_FROM | IN_MOVED_TO)          /* Moves.  */
/* Special flags.  */
#define IN_ONLYDIR       0x01000000     /* Only watch the path if it is a
                                           directory.  */
#define IN_DONT_FOLLOW   0x02000000     /* Do not follow a sym link.  */
#define IN_EXCL_UNLINK   0x04000000     /* Exclude events on unlinked
                                           objects.  */
#define IN_MASK_ADD      0x20000000     /* Add to the mask of an already
#define IN_ONESHOT       0x80000000     /* Only send event once.  */
/* All events which a program can wait on.  */
#define IN_ALL_EVENTS    (IN_ACCESS | IN_MODIFY | IN_ATTRIB | IN_CLOSE_WRITE
                          | IN_CLOSE_NOWRITE | IN_OPEN | IN_MOVED_FROM
                          | IN_MOVED_TO | IN_CREATE | IN_DELETE
                          | IN_DELETE_SELF | IN_MOVE_SELF)

监控制定目录下面创建文件和目录

#include 
#include 
#include 
#include 
#include 
#define	EVENT_SIZE ( sizeof(struct inotify_event) )
#define	BUFF_LEN ( 1024 * ( EVENT_SIZE + 16 ))
int main(void)
{
    int	length, i = 0;
    int	fd;
    int	wd;
    char	buff[BUFF_LEN];
    fd = inotify_init();
    if ( fd < 0) {
        perror("inotify_init error:");
        exit(-1);
    }
    wd = inotify_add_watch(fd, "/home/key1088/code/c/test", IN_CREATE);
    struct inotify_event *event;
    while ( 1 ) {
        memset(buff, 0x00, sizeof(buff));
        length = read(fd, buff, BUFF_LEN);
        if ( length < 0) {
            perror("read:");
        }
        event = ( struct inotify_event * ) &buff[ i ];
        if ( event->len ) {
            if (event->mask & IN_CREATE) {
                if(event->mask & IN_ISDIR) {
                    printf("create dir,dirname=[%s]n", event->name);
                }else{
                    printf("create file,filename=[%s]n", event->name);
                }
            }
        }
    }
    inotify_rm_watch(fd, wd);
    close(fd);
    return 0;
}

参考：http://www.ibm.com/developerworks/cn/linux/l-ubuntu-inotify/

程序设计►C编程

LINUX SYSCALL NUMBER

/usr/include/i386-linux-gnu/asm/unistd.h

# ifdef __i386__
#  include 
# else
#  include 
# endif

/usr/include/i386-linux-gnu/asm/unistd_32.h

#ifndef _ASM_X86_UNISTD_32_H
#define _ASM_X86_UNISTD_32_H
/*
 * This file contains the system call numbers.
 */
#define __NR_restart_syscall      0
#define __NR_exit		  1
#define __NR_fork		  2
#define __NR_read		  3
#define __NR_write		  4
#define __NR_open		  5
#define __NR_close		  6
#define __NR_waitpid		  7
#define __NR_creat		  8
#define __NR_link		  9
#define __NR_unlink		 10
#define __NR_execve		 11
#define __NR_chdir		 12
#define __NR_time		 13
#define __NR_mknod		 14
#define __NR_chmod		 15
#define __NR_lchown		 16
#define __NR_break		 17
#define __NR_oldstat		 18
#define __NR_lseek		 19
#define __NR_getpid		 20
#define __NR_mount		 21
#define __NR_umount		 22
#define __NR_setuid		 23
#define __NR_getuid		 24
#define __NR_stime		 25
#define __NR_ptrace		 26
#define __NR_alarm		 27
#define __NR_oldfstat		 28
#define __NR_pause		 29
#define __NR_utime		 30
#define __NR_stty		 31
#define __NR_gtty		 32
#define __NR_access		 33
#define __NR_nice		 34
#define __NR_ftime		 35
#define __NR_sync		 36
#define __NR_kill		 37
#define __NR_rename		 38
#define __NR_mkdir		 39
#define __NR_rmdir		 40
#define __NR_dup		 41
#define __NR_pipe		 42
#define __NR_times		 43
#define __NR_prof		 44
#define __NR_brk		 45
#define __NR_setgid		 46
#define __NR_getgid		 47
#define __NR_signal		 48
#define __NR_geteuid		 49
#define __NR_getegid		 50
#define __NR_acct		 51
#define __NR_umount2		 52
#define __NR_lock		 53
#define __NR_ioctl		 54
#define __NR_fcntl		 55
#define __NR_mpx		 56
#define __NR_setpgid		 57
#define __NR_ulimit		 58
#define __NR_oldolduname	 59
#define __NR_umask		 60
#define __NR_chroot		 61
#define __NR_ustat		 62
#define __NR_dup2		 63
#define __NR_getppid		 64
#define __NR_getpgrp		 65
#define __NR_setsid		 66
#define __NR_sigaction		 67
#define __NR_sgetmask		 68
#define __NR_ssetmask		 69
#define __NR_setreuid		 70
#define __NR_setregid		 71
#define __NR_sigsuspend		 72
#define __NR_sigpending		 73
#define __NR_sethostname	 74
#define __NR_setrlimit		 75
#define __NR_getrlimit		 76   /* Back compatible 2Gig limited rlimit */
#define __NR_getrusage		 77
#define __NR_gettimeofday	 78
#define __NR_settimeofday	 79
#define __NR_getgroups		 80
#define __NR_setgroups		 81
#define __NR_select		 82
#define __NR_symlink		 83
#define __NR_oldlstat		 84
#define __NR_readlink		 85
#define __NR_uselib		 86
#define __NR_swapon		 87
#define __NR_reboot		 88
#define __NR_readdir		 89
#define __NR_mmap		 90
#define __NR_munmap		 91
#define __NR_truncate		 92
#define __NR_ftruncate		 93
#define __NR_fchmod		 94
#define __NR_fchown		 95
#define __NR_getpriority	 96
#define __NR_setpriority	 97
#define __NR_profil		 98
#define __NR_statfs		 99
#define __NR_fstatfs		100
#define __NR_ioperm		101
#define __NR_socketcall		102
#define __NR_syslog		103
#define __NR_setitimer		104
#define __NR_getitimer		105
#define __NR_stat		106
#define __NR_lstat		107
#define __NR_fstat		108
#define __NR_olduname		109
#define __NR_iopl		110
#define __NR_vhangup		111
#define __NR_idle		112
#define __NR_vm86old		113
#define __NR_wait4		114
#define __NR_swapoff		115
#define __NR_sysinfo		116
#define __NR_ipc		117
#define __NR_fsync		118
#define __NR_sigreturn		119
#define __NR_clone		120
#define __NR_setdomainname	121
#define __NR_uname		122
#define __NR_modify_ldt		123
#define __NR_adjtimex		124
#define __NR_mprotect		125
#define __NR_sigprocmask	126
#define __NR_create_module	127
#define __NR_init_module	128
#define __NR_delete_module	129
#define __NR_get_kernel_syms	130
#define __NR_quotactl		131
#define __NR_getpgid		132
#define __NR_fchdir		133
#define __NR_bdflush		134
#define __NR_sysfs		135
#define __NR_personality	136
#define __NR_afs_syscall	137 /* Syscall for Andrew File System */
#define __NR_setfsuid		138
#define __NR_setfsgid		139
#define __NR__llseek		140
#define __NR_getdents		141
#define __NR__newselect		142
#define __NR_flock		143
#define __NR_msync		144
#define __NR_readv		145
#define __NR_writev		146
#define __NR_getsid		147
#define __NR_fdatasync		148
#define __NR__sysctl		149
#define __NR_mlock		150
#define __NR_munlock		151
#define __NR_mlockall		152
#define __NR_munlockall		153
#define __NR_sched_setparam		154
#define __NR_sched_getparam		155
#define __NR_sched_setscheduler		156
#define __NR_sched_getscheduler		157
#define __NR_sched_yield		158
#define __NR_sched_get_priority_max	159
#define __NR_sched_get_priority_min	160
#define __NR_sched_rr_get_interval	161
#define __NR_nanosleep		162
#define __NR_mremap		163
#define __NR_setresuid		164
#define __NR_getresuid		165
#define __NR_vm86		166
#define __NR_query_module	167
#define __NR_poll		168
#define __NR_nfsservctl		169
#define __NR_setresgid		170
#define __NR_getresgid		171
#define __NR_prctl              172
#define __NR_rt_sigreturn	173
#define __NR_rt_sigaction	174
#define __NR_rt_sigprocmask	175
#define __NR_rt_sigpending	176
#define __NR_rt_sigtimedwait	177
#define __NR_rt_sigqueueinfo	178
#define __NR_rt_sigsuspend	179
#define __NR_pread64		180
#define __NR_pwrite64		181
#define __NR_chown		182
#define __NR_getcwd		183
#define __NR_capget		184
#define __NR_capset		185
#define __NR_sigaltstack	186
#define __NR_sendfile		187
#define __NR_getpmsg		188	/* some people actually want streams */
#define __NR_putpmsg		189	/* some people actually want streams */
#define __NR_vfork		190
#define __NR_ugetrlimit		191	/* SuS compliant getrlimit */
#define __NR_mmap2		192
#define __NR_truncate64		193
#define __NR_ftruncate64	194
#define __NR_stat64		195
#define __NR_lstat64		196
#define __NR_fstat64		197
#define __NR_lchown32		198
#define __NR_getuid32		199
#define __NR_getgid32		200
#define __NR_geteuid32		201
#define __NR_getegid32		202
#define __NR_setreuid32		203
#define __NR_setregid32		204
#define __NR_getgroups32	205
#define __NR_setgroups32	206
#define __NR_fchown32		207
#define __NR_setresuid32	208
#define __NR_getresuid32	209
#define __NR_setresgid32	210
#define __NR_getresgid32	211
#define __NR_chown32		212
#define __NR_setuid32		213
#define __NR_setgid32		214
#define __NR_setfsuid32		215
#define __NR_setfsgid32		216
#define __NR_pivot_root		217
#define __NR_mincore		218
#define __NR_madvise		219
#define __NR_madvise1		219	/* delete when C lib stub is removed */
#define __NR_getdents64		220
#define __NR_fcntl64		221
/* 223 is unused */
#define __NR_gettid		224
#define __NR_readahead		225
#define __NR_setxattr		226
#define __NR_lsetxattr		227
#define __NR_fsetxattr		228
#define __NR_getxattr		229
#define __NR_lgetxattr		230
#define __NR_fgetxattr		231
#define __NR_listxattr		232
#define __NR_llistxattr		233
#define __NR_flistxattr		234
#define __NR_removexattr	235
#define __NR_lremovexattr	236
#define __NR_fremovexattr	237
#define __NR_tkill		238
#define __NR_sendfile64		239
#define __NR_futex		240
#define __NR_sched_setaffinity	241
#define __NR_sched_getaffinity	242
#define __NR_set_thread_area	243
#define __NR_get_thread_area	244
#define __NR_io_setup		245
#define __NR_io_destroy		246
#define __NR_io_getevents	247
#define __NR_io_submit		248
#define __NR_io_cancel		249
#define __NR_fadvise64		250
/* 251 is available for reuse (was briefly sys_set_zone_reclaim) */
#define __NR_exit_group		252
#define __NR_lookup_dcookie	253
#define __NR_epoll_create	254
#define __NR_epoll_ctl		255
#define __NR_epoll_wait		256
#define __NR_remap_file_pages	257
#define __NR_set_tid_address	258
#define __NR_timer_create	259
#define __NR_timer_settime	(__NR_timer_create+1)
#define __NR_timer_gettime	(__NR_timer_create+2)
#define __NR_timer_getoverrun	(__NR_timer_create+3)
#define __NR_timer_delete	(__NR_timer_create+4)
#define __NR_clock_settime	(__NR_timer_create+5)
#define __NR_clock_gettime	(__NR_timer_create+6)
#define __NR_clock_getres	(__NR_timer_create+7)
#define __NR_clock_nanosleep	(__NR_timer_create+8)
#define __NR_statfs64		268
#define __NR_fstatfs64		269
#define __NR_tgkill		270
#define __NR_utimes		271
#define __NR_fadvise64_64	272
#define __NR_vserver		273
#define __NR_mbind		274
#define __NR_get_mempolicy	275
#define __NR_set_mempolicy	276
#define __NR_mq_open 		277
#define __NR_mq_unlink		(__NR_mq_open+1)
#define __NR_mq_timedsend	(__NR_mq_open+2)
#define __NR_mq_timedreceive	(__NR_mq_open+3)
#define __NR_mq_notify		(__NR_mq_open+4)
#define __NR_mq_getsetattr	(__NR_mq_open+5)
#define __NR_kexec_load		283
#define __NR_waitid		284
/* #define __NR_sys_setaltroot	285 */
#define __NR_add_key		286
#define __NR_request_key	287
#define __NR_keyctl		288
#define __NR_ioprio_set		289
#define __NR_ioprio_get		290
#define __NR_inotify_init	291
#define __NR_inotify_add_watch	292
#define __NR_inotify_rm_watch	293
#define __NR_migrate_pages	294
#define __NR_openat		295
#define __NR_mkdirat		296
#define __NR_mknodat		297
#define __NR_fchownat		298
#define __NR_futimesat		299
#define __NR_fstatat64		300
#define __NR_unlinkat		301
#define __NR_renameat		302
#define __NR_linkat		303
#define __NR_symlinkat		304
#define __NR_readlinkat		305
#define __NR_fchmodat		306
#define __NR_faccessat		307
#define __NR_pselect6		308
#define __NR_ppoll		309
#define __NR_unshare		310
#define __NR_set_robust_list	311
#define __NR_get_robust_list	312
#define __NR_splice		313
#define __NR_sync_file_range	314
#define __NR_tee		315
#define __NR_vmsplice		316
#define __NR_move_pages		317
#define __NR_getcpu		318
#define __NR_epoll_pwait	319
#define __NR_utimensat		320
#define __NR_signalfd		321
#define __NR_timerfd_create	322
#define __NR_eventfd		323
#define __NR_fallocate		324
#define __NR_timerfd_settime	325
#define __NR_timerfd_gettime	326
#define __NR_signalfd4		327
#define __NR_eventfd2		328
#define __NR_epoll_create1	329
#define __NR_dup3		330
#define __NR_pipe2		331
#define __NR_inotify_init1	332
#define __NR_preadv		333
#define __NR_pwritev		334
#define __NR_rt_tgsigqueueinfo	335
#define __NR_perf_event_open	336
#define __NR_recvmmsg		337
#define __NR_fanotify_init	338
#define __NR_fanotify_mark	339
#define __NR_prlimit64		340
#define __NR_name_to_handle_at	341
#define __NR_open_by_handle_at  342
#define __NR_clock_adjtime	343
#define __NR_syncfs             344
#define __NR_sendmmsg		345
#define __NR_setns		346
#define __NR_process_vm_readv	347
#define __NR_process_vm_writev	348
#endif /* _ASM_X86_UNISTD_32_H */