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Before writingCodeThe function that reads the system time is often used. The localtime function is not thread-safe. If you call the localtime function in multiple threads, problems may occur. In multi-threaded applications, localtime_r should be

Fix and delete files 1. debugfs Open the partition where the deleted file is located. Open/dev/sda2 2. Use the LS and-D parameters to display the directory of the file you just deleted. Ls-D/root/Data Shown in <> the angle brackets are

1. View commands [Root @ WWW ~] # Sysctl-A | grep local Or CAT/proc/sys/NET/IPv4/ip_local_port_range 2. Modify the port range 1) Permanent modification Add the following line to VI/etc/sysctl. conf: Net. ipv4.ip _ local_port_range = 1024 6

Tcpdump captures TCP identifiers According to each 8-bit group, the TCP flag is located in the 13th 8-bit group, as shown in the following figure. The first row contains 32 digits ranging from 0 to 3 8-bit groups, the second row is a 4-7 eight-bit

Googleperformance toolsIntroduction 1. Installation A) install libunwind Libunwind isProgramThe C ++ library of the Call Stack. Because the built-in stack rollback function of glibc has bugs in 64-bit systems, we recommend that you use

Memcache is a high-performance distributed memory object cache system. By maintaining a unified and huge hash table in the memory, memcache can be used to store data in various formats, including image, video, file, and database retrieval results.

0 introduction with the rapid development of information technology and Internet, information security and reliability issues become increasingly important. Currently, information security is faced with two basic attacks: passive attacks

": X "and ": the true differences between WQ and WQ are as follows: : WQ forcibly writes the file and exits (Save the disk and exit write % quite ). Write the file forcibly even if it is not modified, and update the modification time of the

ExecFunction Family It is called by the exec system. In fact, in Linux, there is no exec () function form. Exec refers to a group of functions, with a total of six functions: # Include Extern char ** environ; Int execl (const char * path,

Use histtimeformat to display the timestamp of the History command After you execute the history command from the command line, only the serial number of the executed command and the command itself are displayed. To view the timestamp of the

in Linux: Generate an empty file of the specified size dd If =/dev/Zero of = m. file BS = 1 m COUNT = 50 the generated file name is M. file empty file, write 50 times, write 1 MB each time;

①Null: defined as 0, 0l, or (void *) 0. It indicates that a pointer value is null, that is, nothing is specified; ②'\ 0': used and only uses the string Terminator., Is a character constant;Nul is the name of a character constant; ③Nul: 0x00,0

Virt: 1. The virtual memory size required by the process, including the database used by the process,Code, Data, as well as the heap space allocated by malloc and new, and the allocated stack space; 2. If the process applies for 10 MB of memory

HTTP request-and response-mode-based, stateless, and application-layer protocols, often based on TCP Connection Methods . HTTP allows transmission of any type of Data Objects , HTTP is a stateless protocol. Stateless means that the Protocol

Working principle of Reverse Proxy Server I plan to study nginx recentlySource codeNginx can be used as a reverse proxy server to achieve load balancing. So I collected some information about the reverse proxy server and sorted it out

clear: Both " Clear floating "clear is often used in CSS. The typical method is clear: Both; This is the description in the CSS manual: the value of this attribute indicates that the edge of a floating object is not allowed. This

1,Use an existing object to construct a non-existing object (which does not exist before the construction), that is, the copy structure. If an existing object is used to overwrite another existing object, the value assignment operation is performed.

pay attention to a symbol extension problem: for example, suppose we want to print the hex representation of the short INTEGER (short)-1 memory. On the Win32 platform, a short type occupies 2 bytes, therefore, we naturally want to print it with four

field separator (FS) is the built-in variable of awk , the default value is blank and tab. awk will first refer to the content of FS for each field cutting. if ":" is also used as a delimiter , awk can automatically separate the hours and

crontab usage considerations 1. use common variables when shell is executed on crontab, only a few system environment variables can be identified, normal variables cannot be identified. If you need to use variables in a script, you need