es上面安装ik分词
./bin/elasticsearch-plugin install https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.4.0/elasticsearch-analysis-ik-7.4.0.zip
返回
-> Downloading https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.4.0/elasticsearch-analysis-ik-7.4.0.zip
分词核心函数
相关阅读
最近在看一个php-cs-fix的时候，发现除了贪婪模式和非贪婪模式还有其他模式 https://github.com/FriendsOfPHP/PHP-CS-Fixer/pull/4659
很好奇explain的时候怎么explain到很多内容的,所以遇到了explain的内容是Impossible ON condition的时候觉得很好奇
代码:
<?php
$code = '<?php echo "string1"."string2"; >';
$tokens = token_get_all($code);
foreach ($tokens as $token) {
if (is_array($token)) {
// 行号、标识符字面量、对应内容
printf("%d - %s\t%s\n", $token[2], token_name($token[0]), $token[1]);
}
}
输出内容:
1 - T_OPEN_TAG <?php
1 - T_ECHO echo
1 - T_WHITESPACE
1 - T_CONSTANT_ENCAPSED_STRING "string1"
1 - T_CONSTANT_ENCAPSED_STRING "string2"
1 - T_WHITESPACE
php-cs-fixer的核心函数是:token_get_all
$tokens = \defined('TOKEN_PARSE')
? token_get_all($code, TOKEN_PARSE)
: token_get_all($code);
调用的核心堆栈:
#0 E:\PHP-CS-Fixer\src\Tokenizer\Tokens.php(222): PhpCsFixer\Tokenizer\Tokens->setCode('<?php\n\n/*\n * Th...')
#1 E:\PHP-CS-Fixer\src\Runner\Runner.php(171): PhpCsFixer\Tokenizer\Tokens::fromCode('<?php\n\n/*\n * Th...')
#2 E:\PHP-CS-Fixer\src\Runner\Runner.php(132): PhpCsFixer\Runner\Runner->fixFile(Object(SplFileInfo), Object(PhpCsFixer\Linter\ProcessLintingResult))
#3 E:\PHP-CS-Fixer\src\Console\Command\FixCommand.php(219): PhpCsFixer\Runner\Runner->fix()
#4 E:\PHP-CS-Fixer\vendor\symfony\console\Command\Command.php(255): PhpCsFixer\Console\Command\FixCommand->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#5 E:\PHP-CS-Fixer\vendor\symfony\console\Application.php(982): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#6 E:\PHP-CS-Fixer\vendor\symfony\console\Application.php(255): Symfony\Component\Console\Application->doRunCommand(Object(PhpCsFixer\Console\Command\FixCommand), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#7 E:\PHP-CS-Fixer\src\Console\Application.php(84): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#8 E:\PHP-CS-Fixer\vendor\symfony\console\Application.php(148): PhpCsFixer\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#9 E:\PHP-CS-Fixer\php-cs-fixer(101): Symfony\Component\Console\Application->run()
#10 {main}
举个例子下面的堆栈:
#0 E:\PHP-CS-Fixer\src\Fixer\Operator\BinaryOperatorSpacesFixer.php(339): PhpCsFixer\Fixer\Operator\BinaryOperatorSpacesFixer->fixWhiteSpaceAroundOperatorToSingleSpace(Object(PhpCsFixer\Tokenizer\Tokens), 19)
#1 E:\PHP-CS-Fixer\src\Fixer\Operator\BinaryOperatorSpacesFixer.php(256): PhpCsFixer\Fixer\Operator\BinaryOperatorSpacesFixer->fixWhiteSpaceAroundOperator(Object(PhpCsFixer\Tokenizer\Tokens), 19)
#2 E:\PHP-CS-Fixer\src\AbstractFixer.php(75): PhpCsFixer\Fixer\Operator\BinaryOperatorSpacesFixer->applyFix(Object(SplFileInfo), Object(PhpCsFixer\Tokenizer\Tokens))
#3 E:\PHP-CS-Fixer\src\Runner\Runner.php(192): PhpCsFixer\AbstractFixer->fix(Object(SplFileInfo), Object(PhpCsFixer\Tokenizer\Tokens))
#4 E:\PHP-CS-Fixer\src\Runner\Runner.php(132): PhpCsFixer\Runner\Runner->fixFile(Object(SplFileInfo), Object(PhpCsFixer\Linter\ProcessLintingResult))
#5 E:\PHP-CS-Fixer\src\Console\Command\FixCommand.php(219): PhpCsFixer\Runner\Runner->fix()
#6 E:\PHP-CS-Fixer\vendor\symfony\console\Command\Command.php(255): PhpCsFixer\Console\Command\FixCommand->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#7 E:\PHP-CS-Fixer\vendor\symfony\console\Application.php(982): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#8 E:\PHP-CS-Fixer\vendor\symfony\console\Application.php(255): Symfony\Component\Console\Application->doRunCommand(Object(PhpCsFixer\Console\Command\FixCommand), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#9 E:\PHP-CS-Fixer\src\Console\Application.php(84): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#10 E:\PHP-CS-Fixer\vendor\symfony\console\Application.php(148): PhpCsFixer\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#11 E:\PHP-CS-Fixer\php-cs-fixer(101): Symfony\Component\Console\Application->run()
#12 {main}
核心就是给后面加入token // todo
创建网桥,可以通过bridge-utils包的brctl来创建一个网桥
$sudo brctl addbr br0
然后通过brctl show可以看到列出的网桥
$brctl show
bridge name bridge id STP enabled interfaces
br0 8000.000000000000 no
通过strace查看系统调用
$sudo strace brctl addbr br1
输出
ubuntu@VM-0-3-ubuntu:~/libnlbuild/bin$ sudo strace brctl addbr br1
...
socket(AF_UNIX, SOCK_STREAM, 0) = 3
ioctl(3, SIOCBRADDBR, "br1") = 0
+++ exited with 0 +++
看到调用
ioctl(3, SIOCBRADDBR, "br1")
3 指的是打开的文件描述符.0,1,2都是特殊的标准输入输出错误等的文件描述符,所以下一个打开的文件就是3
我写的一个创建网桥的小例子
// bradd.c
#include <linux/sockios.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <stdio.h>
int main(){
int br_socket_fd,ret;
if(br_socket_fd = socket(AF_LOCAL, SOCK_STREAM, 0) < 0){
perror("Error: ");
}
if(ret = ioctl(br_socket_fd, SIOCBRADDBR,"hello") < 0) // SIOCBRADDBR 由sockios.h 引入
{
perror("ioctl error");
}
return 0;
}
$gcc bradd.c -o
## 需要使用sudo添加网桥
$sudo ./bradd
然后用brctl show 输出,创建了一个叫hello的网桥:
$ brctl show
bridge name bridge id STP enabled interfaces
docker0 8000.024273119fd1 no vethe6cf6a0
hello 8000.000000000000 no
然后我们发现了docker0和hello两个网桥相差一个interfaces,我们如何添加veth呢?
brctl addifint br_add_interface(const char *bridge, const char *dev)
{
struct ifreq ifr;
...
int ifindex = if_nametoindex(dev);
...
strncpy(ifr.ifr_name, bridge, IFNAMSIZ);
ifr.ifr_ifindex = ifindex;
err = ioctl(br_socket_fd, SIOCBRADDIF, &ifr);
...
}
最后调用linux 的net/bridge/br_if.c:
// dev 是我们要添加的设备 // br 是我们的网桥
/* called with RTNL */
int br_add_if(struct net_bridge *br, struct net_device *dev,
struct netlink_ext_ack *extack)
{
struct net_bridge_port *p;
int err = 0;
unsigned br_hr, dev_hr;
bool changed_addr;
...
p = new_nbp(br, dev);
if (IS_ERR(p))
return PTR_ERR(p);
call_netdevice_notifiers(NETDEV_JOIN, dev);
err = dev_set_allmulti(dev, 1);
if (err) {
kfree(p); /* kobject not yet init'd, manually free */
goto err1;
}
err = kobject_init_and_add(&p->kobj, &brport_ktype, &(dev->dev.kobj),
SYSFS_BRIDGE_PORT_ATTR);
if (err)
goto err2;
err = br_sysfs_addif(p);
if (err)
goto err2;
err = br_netpoll_enable(p);
if (err)
goto err3;
err = netdev_rx_handler_register(dev, br_handle_frame, p);
if (err)
goto err4;
dev->priv_flags |= IFF_BRIDGE_PORT;
err = netdev_master_upper_dev_link(dev, br->dev, NULL, NULL, extack);
if (err)
goto err5;
err = nbp_switchdev_mark_set(p);
if (err)
goto err6;
dev_disable_lro(dev);
list_add_rcu(&p->list, &br->port_list);
nbp_update_port_count(br);
netdev_update_features(br->dev);
br_hr = br->dev->needed_headroom;
dev_hr = netdev_get_fwd_headroom(dev);
if (br_hr < dev_hr)
update_headroom(br, dev_hr);
else
netdev_set_rx_headroom(dev, br_hr);
if (br_fdb_insert(br, p, dev->dev_addr, 0))
netdev_err(dev, "failed insert local address bridge forwarding table\n");
if (br->dev->addr_assign_type != NET_ADDR_SET) {
/* Ask for permission to use this MAC address now, even if we
* don't end up choosing it below.
*/
err = dev_pre_changeaddr_notify(br->dev, dev->dev_addr, extack);
if (err)
goto err7;
}
err = nbp_vlan_init(p, extack);
if (err) {
netdev_err(dev, "failed to initialize vlan filtering on this port\n");
goto err7;
}
spin_lock_bh(&br->lock);
changed_addr = br_stp_recalculate_bridge_id(br);
if (netif_running(dev) && netif_oper_up(dev) &&
(br->dev->flags & IFF_UP))
br_stp_enable_port(p);
spin_unlock_bh(&br->lock);
br_ifinfo_notify(RTM_NEWLINK, NULL, p);
if (changed_addr)
call_netdevice_notifiers(NETDEV_CHANGEADDR, br->dev);
br_mtu_auto_adjust(br);
br_set_gso_limits(br);
kobject_uevent(&p->kobj, KOBJ_ADD);
return 0;
...
}
添加虚拟设备:
# strace ip link add vethaaa type veth peer name vethbbb
execve("/sbin/ip", ["ip", "link", "add", "vethaaa", "type", "veth", "peer", "name", "vethbbb"], 0x7ffed8af30f0 /* 23 vars */)
...
socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
setsockopt(3, SOL_SOCKET, SO_SNDBUF, [32768], 4) = 0
setsockopt(3, SOL_SOCKET, SO_RCVBUF, [1048576], 4) = 0
setsockopt(3, SOL_NETLINK, NETLINK_EXT_ACK, [1], 4) = 0
bind(3, {sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, nl_pid=26226, nl_groups=00000000}, [12]) = 0
sendto(3, {{len=32, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK, seq=0, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}}, 32, 0, NULL, 0) = 32
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base={{len=52, type=NLMSG_ERROR, flags=0, seq=0, pid=26226}, {error=-ENODEV, msg={{len=32, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK, seq=0, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}}}}, iov_len=16384}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 52
access("/proc/net", R_OK) = 0
access("/proc/net/unix", R_OK) = 0
socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0) = 4
ioctl(4, SIOCGIFINDEX, {ifr_name="vethaaa"}) = -1 ENODEV (No such device)
close(4) = 0
brk(NULL) = 0x560e12455000
brk(0x560e12476000) = 0x560e12476000
openat(AT_FDCWD, "/usr/lib/ip/link_veth.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base={{len=92, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1576836139, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}, [{{nla_len=12, nla_type=IFLA_IFNAME}, "vethaaa"}, {{nla_len=48, nla_type=IFLA_LINKINFO}, [{{nla_len=8, nla_type=IFLA_INFO_KIND}, "veth"...}, {{nla_len=36, nla_type=IFLA_INFO_DATA}, "\x20\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0c\x00\x03\x00\x76\x65\x74\x68\x62\x62\x62\x00"}]}]}, iov_len=92}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 92
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base=NULL, iov_len=0}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_TRUNC}, MSG_PEEK|MSG_TRUNC) = 36
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base={{len=36, type=NLMSG_ERROR, flags=NLM_F_CAPPED, seq=1576836139, pid=26226}, {error=0, msg={len=92, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1576836139, pid=0}}}, iov_len=36}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 36
socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
setsockopt(3, SOL_SOCKET, SO_SNDBUF, [32768], 4) = 0
setsockopt(3, SOL_SOCKET, SO_RCVBUF, [1048576], 4) = 0
setsockopt(3, SOL_NETLINK, NETLINK_EXT_ACK, [1], 4) = 0
bind(3, {sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, nl_pid=18263, nl_groups=00000000}, [12]) = 0
sendto(3, {{len=32, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK, seq=0, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}}, 32, 0, NULL, 0) = 32
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base={{len=52, type=NLMSG_ERROR, flags=0, seq=0, pid=18263}, {error=-EPERM, msg={{len=32, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK, seq=0, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}}}}, iov_len=16384}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 52
access("/proc/net", R_OK) = 0
access("/proc/net/unix", R_OK) = 0
socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0) = 4
ioctl(4, SIOCGIFINDEX, {ifr_name="p1"}) = -1 ENODEV (No such device)
close(4) = 0
brk(NULL) = 0x5595d01bb000
brk(0x5595d01dc000) = 0x5595d01dc000
openat(AT_FDCWD, "/usr/lib/ip/link_veth.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base={{len=84, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1576748752, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}, [{{nla_len=7, nla_type=IFLA_IFNAME}, "p1"}, {{nla_len=44, nla_type=IFLA_LINKINFO}, [{{nla_len=8, nla_type=IFLA_INFO_KIND}, "veth"...}, {{nla_len=32, nla_type=IFLA_INFO_DATA}, "\x1c\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x07\x00\x03\x00\x70\x32\x00\x00"}]}]}, iov_len=84}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 84
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base=NULL, iov_len=0}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_TRUNC}, MSG_PEEK|MSG_TRUNC) = 104
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base={{len=104, type=NLMSG_ERROR, flags=0, seq=1576748752, pid=18263}, {error=-EPERM, msg={{len=84, type=RTM_NEWLINK, flags=NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE, seq=1576748752, pid=0}, {ifi_family=AF_UNSPEC, ifi_type=ARPHRD_NETROM, ifi_index=0, ifi_flags=0, ifi_change=0}, [{{nla_len=7, nla_type=IFLA_IFNAME}, "p1"}, {{nla_len=44, nla_type=IFLA_LINKINFO}, [{{nla_len=8, nla_type=IFLA_INFO_KIND}, "veth"...}, {{nla_len=32, nla_type=IFLA_INFO_DATA}, "\x1c\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x07\x00\x03\x00\x70\x32\x00\x00"}]}]}}}, iov_len=104}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 104
write(2, "RTNETLINK answers: Operation not"..., 43RTNETLINK answers: Operation not permitted
) = 43
exit_group(2) = ?
+++ exited with 2 +++
linux 相关的netlink veth内容:
// drivers\net\veth.c
static struct rtnl_link_ops veth_link_ops = {
.kind = DRV_NAME,
.priv_size = sizeof(struct veth_priv),
.setup = veth_setup,
.validate = veth_validate,
.newlink = veth_newlink,
.dellink = veth_dellink,
.policy = veth_policy,
.maxtype = VETH_INFO_MAX,
.get_link_net = veth_get_link_net,
};
E:\linux-master\net\netlink\af_netlink.c
static const struct proto_ops netlink_ops = {
.family = PF_NETLINK,
.owner = THIS_MODULE,
.release = netlink_release,
.bind = netlink_bind,
.connect = netlink_connect,
.socketpair = sock_no_socketpair,
.accept = sock_no_accept,
.getname = netlink_getname,
.poll = datagram_poll,
.ioctl = netlink_ioctl,
.listen = sock_no_listen,
.shutdown = sock_no_shutdown,
.setsockopt = netlink_setsockopt,
.getsockopt = netlink_getsockopt,
.sendmsg = netlink_sendmsg,
.recvmsg = netlink_recvmsg,
.mmap = sock_no_mmap,
.sendpage = sock_no_sendpage,
};
首先是添加socket
(gdb) bt
#0 socket () at ../sysdeps/unix/syscall-template.S:78
#1 0x00005555555b60c7 in rtnl_open_byproto (rth=0x5555557d8020 <rth>, subscriptions=0, protocol=<optimized out>) at libnetlink.c:194
#2 0x000055555555f956 in main (argc=9, argv=0x7fffffffe548) at ip.c:308
Breakpoint 6, __libc_sendmsg (fd=3, msg=msg@entry=0x7fffffffdd70, flags=flags@entry=0) at ../sysdeps/unix/sysv/linux/sendmsg.c:28
28 ../sysdeps/unix/sysv/linux/sendmsg.c: No such file or directory.
(gdb) bt
#0 __libc_sendmsg (fd=3, msg=msg@entry=0x7fffffffdd70, flags=flags@entry=0) at ../sysdeps/unix/sysv/linux/sendmsg.c:28
#1 0x00005555555b5c8f in __rtnl_talk_iov (rtnl=0x5555557d8020 <rth>, iov=iov@entry=0x7fffffffddf0, iovlen=iovlen@entry=1, answer=answer@entry=0x0, show_rtnl_err=show_rtnl_err@entry=true,
errfn=0x0) at libnetlink.c:887
#2 0x00005555555b7225 in __rtnl_talk (errfn=0x0, show_rtnl_err=true, answer=<optimized out>, n=0x7fffffffde40, rtnl=<optimized out>) at libnetlink.c:1000
#3 rtnl_talk (rtnl=<optimized out>, n=n@entry=0x7fffffffde40, answer=answer@entry=0x0) at libnetlink.c:1006
#4 0x000055555557bc6e in iplink_modify (cmd=cmd@entry=16, flags=flags@entry=1536, argc=3, argc@entry=6, argv=<optimized out>, argv@entry=0x7fffffffe560) at iplink.c:1084
#5 0x000055555557c0c6 in do_iplink (argc=7, argv=0x7fffffffe558) at iplink.c:1641
#6 0x000055555555ff0c in do_cmd (argv0=0x7fffffffe7d8 "link", argc=8, argv=0x7fffffffe550) at ip.c:113
#7 0x000055555555f9a0 in main (argc=9, argv=0x7fffffffe548) at ip.c:317
比如命令ip link add veth_0 type veth peer name veth_0_peer
初始化的时候req.n 的长度是32
p req.n.nlmsg_len
$1 = 32
经过ret = iplink_parse(argc, argv, &req, &type); 后变成44,
(gdb) p ((char *)n)[32]@64
$50 = "\v\000\003\000veth_0\000\000\064\000\022\000\b\000\001\000veth(\000\002\000$\000\001", '\000' <repeats 17 times>, "\020\000\003\000veth_0_peer"
# type iptables
iptables is hashed (/sbin/iptables)
iptables命令为什么可以处理那些问题呢？
iptable就是通过socket netlink做特别的通信,改变netfilter子系统的相关hook
import java.io.*;
public class className
{
public void deposit(double amount) throws RemoteException
{
// Method implementation
throw new RemoteException();
}
//Remainder of class definition
}
实质就是一个获取堆栈的类,这个类特别的地方在于可以获取堆栈,核心也在于获取堆栈和捕获异常
The unchecked exception classes are the run-time exception classes and the error classes.
The checked exception classes are all exception classes other than the unchecked exception classes. That is, the checked exception classes are Throwable and all its subclasses other than RuntimeException and its subclasses and Error and its subclasses.
uncheckded exception就是运行时异常类和error类,其他都是checked exception
版本是java8
java的string是什么呢? 很明显是对象
15.18.1. String Concatenation Operator + If only one operand expression is of type String, then string conversion (§5.1.11) is performed on the other operand to produce a string at run time. 来源
java的字符串连接符是+,而php的是.
由于上面提到的jls8中的String Concatenation Operator +提到相关内容,如果操作符中只有一个string类型的话,类型转换会发生在运行时.没有规定两个都是string的时候怎么处理,所以javac将他折叠了
/** If tree is a concatenation of string literals, replace it
* by a single literal representing the concatenated string.
*/
protected JCExpression foldStrings(JCExpression tree) {
if (!allowStringFolding)
return tree;
ListBuffer<JCExpression> opStack = new ListBuffer<>();
ListBuffer<JCLiteral> litBuf = new ListBuffer<>();
boolean needsFolding = false;
JCExpression curr = tree;
while (true) {
if (curr.hasTag(JCTree.Tag.PLUS)) {
JCBinary op = (JCBinary)curr;
needsFolding |= foldIfNeeded(op.rhs, litBuf, opStack, false);
curr = op.lhs;
} else {
needsFolding |= foldIfNeeded(curr, litBuf, opStack, true);
break; //last one!
}
}
if (needsFolding) {
List<JCExpression> ops = opStack.toList();
JCExpression res = ops.head;
for (JCExpression op : ops.tail) {
res = F.at(op.getStartPosition()).Binary(optag(TokenKind.PLUS), res, op);
storeEnd(res, getEndPos(op));
}
return res;
} else {
return tree;
}
看到phpstorm的相关警告,经常会看到phpstorm会警告没有ext-json,我才最近发现composer.json会添加相关的扩展校验.
举个例子
"require": {
"php": ">=5.4.0",
"topthink/framework": "^5.0",
"php-imap/php-imap": "~2.0",
"phpoffice/phpspreadsheet": "^1.3",
"hprose/hprose": "^2.0",
"ext-json": "*" // 这就是解析require json 扩展
},
这个就是校验是否含有json扩展,那么composer是怎么实现的呢?其实是通过extension_loaded这个函数取查看扩展版本的
实现是在composer的129行实现,通过extension_loaded获取扩展.
写了很久的php的原生代码,对php相对路径自动加载这类坑的恐惧已经深入骨髓了.
java和golang也有类似的内容,对于写java没多久的我来说,先记录一下
关于类名和classpath的关系,oracle的文档有相关的描述
Class Path and Package Names
Java classes are organized into packages that are mapped to directories in the file system. But, unlike the file system, whenever you specify a package name, you specify the whole package name and never part of it. For example, the package name for java.awt.Button is always specified as java.awt.
For example, suppose you want the JRE to find a class named Cool.class in the package utility.myapp. If the path to that directory is /java/MyClasses/utility/myapp, then you would set the class path so that it contains /java/MyClasses. To run that application, you could use the following java command:
java -classpath /java/MyClasses utility.myapp.Cool When the application runs, the JVM uses the class path settings to find any other classes defined in the utility.myapp package that are used by the Cool class.
The entire package name is specified in the command. It is not possible, for example, to set the class path so it contains /java/MyClasses/utility and use the command java myapp.Cool. The class would not be found.
You might wonder what defines the package name for a class. The answer is that the package name is part of the class and cannot be modified, except by recompiling the class.
首先说编译:
查看javac 的帮助:
javac --help
Usage: javac <options> <source files>
javac 的参数是:
javac+文件路径
举个例子: 现在在com的上一级目录上
下面是HelloWorld.java的代码
package com.helloworld;
public class HelloWorld
{
static public int m = 1;
public int i = 1;
}
# ls
com
# tree
.
└── com
└── helloworld
└── HelloWorld.java
我要怎么编译com/hellowrld/HelloWorld.java下面的文件呢?
这么编译就可以了:
javac com/helloworld/*.java
然后看一下目录树,在下面多了一个class文件
# tree
.
└── com
└── helloworld
├── HelloWorld.class
└── HelloWorld.java
重新开始,我们看看-d 这个参数有什么用:
# mkdir classes
# tree
.
├── classess
└── com
└── helloworld
└── HelloWorld.java
那么我们编译之后会在设置的-d的目录里面添加相关目录:
# javac -d ./classes/ com/helloworld/*.java
# tree
.
├── classes
│ └── com
│ └── helloworld
│ └── HelloWorld.class
├── classess
└── com
└── helloworld
└── HelloWorld.java