Commonly used condition judgment in linuxShell

Commonly used condition judgment in linuxShell-bfile if the file exists and is a special block file, it is true-cfile if the file exists and is a special character file, true-dfile if the file exists and is a directory, it is true-e... information & nbsp; | & nbsp common condition judgment in linux Shell-B file if the file exists and is a special file, true-c file if the file exists and is a special character file, true-d file if the file exists and is a directory, true-e file if the file exists, true-f file if the file exists and is a rule file, true-g file if the file exists and the SGID bit value is set, true-h file. if the file exists and is a conforming link, true-k file if the file exists and the "sticky" bit value is set-p file if the file exists and is a named pipe, true-r file if the file exists and is readable, true-s file: If the file exists and its size is greater than zero, it is true-u fi. Le if the file exists and the SUID bit is set, true-w file if the file exists and can be written, true-x file if the file exists and can be executed, true-o file if the file exists and is owned by the valid user ID, true-z string if the string length is 0, true-n string if the string length is not 0, it is true string1 = string2 if the two strings are equal, it is true string1! = String2 if the two strings are not equal, true int1-eq int2 if int1 is equal to int2, true int1-ne int2 if int1 is not equal to int2, true int1-lt int2 if int1 is smaller than int2, true int1-le int2 if int1 is smaller than or equal to int2, true int1-gt int2 if int1 is greater than int2, true int1-ge int2 if int1 is greater than or equal to int2, true! If expr is false, the composite expression is true. Expr can be any valid test expression expr1-a expr2 if both expr1 and expr2 are true, the entire formula is true expr1-o expr2 if expr1 and expr2 are true, the entire formula is true. the special variable $0 is name of the executed command. For shell scripts, this is the path of the activated command $ n. This variable corresponds to the parameters included when the script is activated. N is a positive integer corresponding to the parameter location ($1, $2 ...) $ # Provide the script parameter number $ * all these parameters are enclosed by double quotation marks. If a script receives two parameters, $ * equals to $1 $2 $ @. all these parameters are enclosed in double quotation marks. If a script receives two parameters, $ @ is equivalent to $1 $2 $? Exit status after the previous command is executed $ process number of the current shell. For a shell script, this is the ID of the process in progress $! Process Number of the previous background command