Shell Step by Step (3)--stdin & If

4. Input and output

#! /bin/bash# Read users input and then get his nameread"Please input your first name: " firstNameread"Please input your last name: " lastNameecho-e"Your full name is:   $firstName  $lastName"

Read how to use:

read[-ers][-a 数组][-d 分隔符][-i 缓冲区文字]      [-n 读取字符数][-N 读取字符数][-p 提示符]      [-t 超时][-u 文件描写叙述符][名称 ...]

5. Conditional discriminant Formula

- eIs there a-nt (newer than) file1 is better than file2 new-ot (older than) file1 than file2 old-neIndicates not equal to-eqEquals, as:if["$a" -eq "$b"]-neNot equal to, as:if["$a" -ne "$b"]-GTGreater than, as:if["$a" -GT "$b"]-ge is greater than or equal to, such as:if["$a"-ge"$b"]-ltLess than, such as:if["$a" -lt "$b"]-le less than equals, such as:if["$a"-le"$b"]< is less than (requires double brackets), such as: (("$a"<"$b") <= is less than or equal (requires double brackets), such as: (("$a"<="$b") > Greater than (requires double brackets), such as: (("$a">"$b") >= is greater than or equal to (requires double brackets), such as: (("$a">="$b")-Z (zero)

[-AFILE] SupposeFILEThe existence is true. [-BFILE] SupposeFILEExists and is a block special file is true. [-CFILE] SupposeFILEexists and is a word special file is true. [-DFILE] SupposeFILEexists and is a folder is true. [-EFILE] SupposeFILEThe existence is true.
[-F file ]  assumes that file exists and is a normal file true.
[-G file ] assumes that FILE exists and that Sgid is set to true. [-H file ] assumes that file exists and is a symbolic connection true.
[-K file ] is true if file exists and the sticky bit has been set. [-P FILE ] assumes that file exists and is a name pipe (f assumes O) is true.
[-R file ] is true if file exists and is readable. [-S file ] assumes that file exists and the size is not 0 true. [-T FD] assumes that the file Description descriptor FD is open and pointing to a terminal is true. [-U FILE ] assumes that file exists and that suid (set user ID) is true. [-W file ] assumes that file is true if file exists and is writable.
[-X FILE ] is true if file exists and is operational.
[-O FILE ] assumes that file exists and is valid user ID is true. [-G file ] is true if file exists and is a valid user group. [-L file ] assumes that file exists and is a symbolic connection true.
[-N file ] assumes that  the FILE exists and has been MoD assumes that the IED since it is last read is true. [-S file ] assumes that file exists and is a socket true.

[File1-nt FILE2] assumes FILE1 have been changed more recently than FILE2,orSuppose FILE1 exists andFILE2does  notIs true. [File1-ot FILE2] assumes FILE1 is older than FILE2, or FILE2 exists and FILE1 does not exist.
[File1-ef FILE2] assumes that FILE1 and FILE2 point to the same device and the node number is true. [-O Optionname] assumes that the shell option "Optionname" is turned on for true. [-Z STRING] "STRING" is true if the length is zero. [-N STRING] or [STRING] The length of "STRING" is not 0 Non-zero is true. [STRING1 = = STRING2] Assume that 2 strings are the same. "=" May is used instead of "= =  " for strict POSIX Complianc E is true. [STRING1! = STRING2] assumes that the string is not equal to true.
[STRING1 < STRING2] assumes "STRING1" sorts before "STRING2" lexicographically in  c1>  The current locale is true.
[STRING1 > STRING2] assumes "STRING1" sorts After"STRING2" lexicographicallyinch  theThe current locale is true. [ARG1 OP ARG2] "OP" isOne of-eq,-ne,-lt,-le,-GTor-ge. These arithmetic binary operatorsreturn true if"ARG1" is Equal  to, not Equal  to,Less than, less thanor Equal  to,Greater than,or Greater than or Equal  to"ARG2", respectively. "ARG1" and"ARG2" is integers.

e.g:

if"$UID"-ne"$ROOT_UID" ]  then ……

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Shell Step by Step (3)--stdin & If