set user id

1. Arithmetic operators2. Relational operators3. Boolean operator4. String operator5. FILE-related operatorsArithmetic operatorsThe bash shell does not provide any mechanism to perform simple arithmetic operations, but we can use some other programs,

When I wrote makefile on my CentOs7.1 yesterday, I found that a C program made an error when compiling and linking a generated LIB dynamic library. The link command is probably like this:[[email protected] tcpmsg]# gcc -o hello main.c

1. Password Security The/etc/passwd file in UNIX systems contains information about each user that all systems need to know (the encrypted password may also be stored in the/etc/shadow file ). /Etc/passwd contains the user's login name, encrypted

The most commercial version was successfully upgraded last time. The next step is to integrate the company's community website. First, let us know where I am working is a local community website, and PHPWind is used as the basic program, my task is

A few days ago, I encountered a strange problem in the management system. Today I have the opportunity to install the MySQL environment to reproduce this problem. Because it is not the most primitive environment, it may not be completely reproduced,

We know that the development of networks is inseparable from the sharing of resources. In this case, we use the NFS protocol for sharing. Pay attention to the security issues of NFS servers. NFS is short for Network File System. It is an integral

1. system functions # Include INT system (const char * cmd ); If CMD is a null pointer, system returns a non-zero value only when the command handler is available. Because system calls fork, exec, and waitpid in its implementation, there are three

1.3. popen and pclose Functions The standard I/O Library provides two functions: popen and pclose. The two functions implement the following operations: Create an MPS queue, call fork to generate a sub-process, close the Non-Use end of the MPs queue,

  Prototype: int mkdir (const char * filename, mode_t Mode)If the return value is 0, the operation is successful. If the return value is-1, an error occurs. To use this function, you must

There are two methods to obtain the file size: Method 1, Example: Unsigned long get_file_size (const char * path) { unsigned long filesize =-1; file * FP; fp = fopen (path, "R"); If (FP = NULL) return filesize; fseek (FP, 0l, seek_end);

1. Test the file access permission.   # Include Define the function int access (const char * pathname, int mode );Function Description: Access () checks whether an existing file can be read/written. The mode parameter can be combined in several

Chapter 5 5.5 Linux system call 5.5.1 System Call Interface System calls (commonly referred to as syscils) are the only interface for interaction between linux kernels and upper-layer applications. See Figure 5-4. According to the description of

Intchmod (const char *, mode_t)/* file mode * // * read, write, execute/search by owner */# assets/* [xsi] rwx mask for owner */# defines_irusr0000400/* [xsi] r for owner */# defines_iwusr0000200/* [xsi] W for owner */# defines_ixusr0000100/* [xsi]

Code: Mkdir function in Linux   Prototype: int mkdir (const char * filename, mode_t Mode) If the return value is 0, the operation is successful. If the return value is-1, an error occurs. This function must contain header files. #

From http://blog.csdn.net/linuxgroup In Linux, I always encounter a headache because I don't have the permission to modify files. As a newbie, I like "chmod 777-r file directory". As a result, the system crashes. " ChmodCommand Purpose

Lien0000342014-09-101. file access permission In File Access Permissions and process access control, we have already talked about the file access limit. For convenience, we recolumn it below,   Table 1: 9 access limit of a file

1. switch from the current user to the root user: directly enter the su command, and then enter the root password. If you have not set the root command password before, the login will fail. Here, you need to run the sudo passwd command to set the

Address: http://www.examw.com/linux/all/114976/index.html Test command usage. Function: Checks files and comparison values. 1) judgment Expression If test (expression true) If test! The expression is false. Test expression 1-A expression 2 both are

3) getting started with Linux programming-File OperationsFile Operations in LinuxPreface:In this section, we will discuss various functions for file operations in Linux.File Creation and read/writeFile AttributesDirectory file operationsMPs queue

The mkdir function in Linux-general Linux technology-Linux programming and kernel information. The following is a detailed description. Prototype: int mkdir (const char * filename, mode_t mode) If the return value is 0, the operation is successful.