Quick query of Linux Shell syntax

Quick query of Linux Shell syntax compiled by myself (comparison using C language syntax)

Although I have learned Linux Shell programming, there are only a few chance to write shell scripts (usually I write more when setting up a development environment in the early stage of the project ), as a result, some syntaxes will be forgotten over time. The efficiency of reading a simple syntax is really slow, so I sorted out a table, since the programming language I use is C/C ++, the first thing that comes to mind in programming is how to write it in C language, so I will simply compare the C language syntax with the shell programming syntax, so that it is convenient to query it. HA:

 

(Note: I do not know why the pasted table in the word is not completely displayed here, and it is normal during editing)

 

 

Functions to be implemented	C Programming	Linux Shell Script Programming
Passing Program/Script Parameters	Int main (INT argc, char ** argv) { If (argv! = 4 ){ Printf ("Usage: % s arg1 arg2 arg3", argv [0]); Return 1; }   Printf ("arg1: % s \ n", argv [1]); Printf ("arg2: % s \ n", argv [2]); Printf ("arg3: % s \ n", argv [3]); Return 0; }	#! /Bin/sh   If [$ #-lt 3]; then Echo "Usage: 'basename $ 0' arg1 arg2 arg3"> & 2 Exit 1 Fi   Echo "arg1: $1" Echo "arg2: $2" Echo "arg3: $3" Exit 0
	Int main (INT argc, char ** argv) { Int I; For (I = 1; I <= argc; I ++ ){ Printf ("Arg: % s \ n", argv [I]); } Return 0; }	#! /Bin/sh   While [$ #-Ne 0] Do Echo "Arg: $1" Shift Done
Logical/numeric operations	If (D = 0)	If ["$ D"-EQ "0"]; then
	If (D! = 0)	If ["$ D"-ne "0"]; then
	If (D> 0)	If ["$ D"-GT "0"]; then
	If (d <0)	If ["$ D"-lt "0"]; then
	If (d <= 0)	If ["$ D"-Le "0"]; then
	If (D> = 0)	If ["$ D"-ge "0"]; then
String comparison	If (strcmp (STR, "ABC") = 0 ){ }	If ["$ Str "! = "ABC"]; then Fi
Input and Output	Scanf ("% d", & D );	Read d
	Printf ("% d", d );	Echo-N $ d
	Printf ("% d", d );	Echo $ d
	Printf ("press any to continue ..."); Char CH = getchar (); Printf ("\ Nyou pressed: % C \ n", CH );	#! /Bin/sh   Getchar () { Savedtty = 'stty-G' Stty cbreak Dd If =/dev/tty BS = 1 COUNT = 1 2>/dev/null Stty-cbreak Stty $ savedtty }   Echo-n "press any key to continue ..." Ch = 'getchar' Echo "" Echo "you pressed: $ ch"
		Read d <& 3
Procedures for controlling programs and scripts	If (isok ){ // 1 } Else if (isok2 ){ // 2 } Else { // 3 }	If [isok]; then #1 Elif [isok2]; then #2 Else #3 Fi
	Switch (d) { Case 1: Printf ("you select 1 \ n "); Break; Case 2: Case 3: Printf ("you select 2 or 3 \ n "); Break; Default: Printf ("error \ n "); Break; };	Case $ D in 1) echo "you select 1" ;; 2 | 3) echo "you select 2 or 3" ;; *) Echo "error" ;; Esac
	For (INT loop = 1; loop <= 5; loop ++ ){ Printf ("% d", loop ); }	For Loop in 1 2 3 4 5 Do Echo $ Loop Done
	Do { Sleep (5 ); } While (! Isroot );	Is_root = 'who | grep root' Until ["$ is_root"] Do Sleep 5 Done
	Counter = 0; While (counter <5 ){ Printf ("% d \ n", counter ); Counter ++; }	Counter = 0 While [$ counter-lt 5] Do Echo $ counter Counter = 'expr $ counter + 1' Done
	While (1 ){ }	While: Do Done
	Break;	Break or break N, N indicates that the n-level loop exists.
	Continue;	Continue
Function and Process Definition	Void Hello () { Printf ("Hello \ n "); } ... // Function call Hello ();	Hello () { Echo "Hello" } Or Function Hello () { Echo "Hello" } ... # Function call Hello
Function parameters and return values	Int ret = doit (); If (ret = 0 ){ Printf ("OK \ n "); }	Doit If ["$ ?" -EQ 0]; then Echo "OK" Fi Or Ret = doit If ["$ RET"-EQ "0"]; then Echo "OK" Fi
	Int sum (int A, int B) { Return A + B; } Int S = sum (1, 2 ); Printf ("the sum is: % d \ n", S );	Sum () { Echo-n "'expr $1 + $2 '" } S = 'sum 1 2' Echo "the sum is: $ S"
	Bool isok () {return false ;} If (isok ){ Printf ("Yes \ n "); } Else { Printf ("No \ n "); }	Isok () { Return 1; } If isok; then Echo "yes" Else Echo "no" Fi