7. Bash 中的 if ## FORMAT if [ condition ]; then cmd elif [ condition ]; then cmd else cmd fi ## EXAMPLE if [ -e file1 ] # file1 exists if [ -f file1 ] # file1 exists and is a regular file if [ -s file1 ] # file1
is placed before a command or condition. If the command or condition returns a failure (non-zero exit status), the!negates it and makes theifcondition true. The!operator is typically used with commands or test expressions to perform a logical negation. If the command returns false, the nega...
参数可以是以下任意一项:-e: Returns true value, if file exists -f: Return true value, if file exists and regular file -r: Return true value, if file exists and is readable -w: Return true value, if file exists and is writable -x: Return true value, if file exists and is executable...
Theifstatement is closed with afi(reverse of if). Pay attention to white space! There must be a space between the opening and closing brackets and the condition you write. Otherwise, the shell will complain of error. There must be space before and after the conditional operator (=, ==, ...
-ne 不等于,如:if [ "a"−ne"b" ] -gt 大于,如:if [ "a"−gt"b" ] -ge 大于等于,如:if [ "a"−ge"b" ] -lt 小于,如:if [ "a"−lt"b" ] -le 小于等于,如:if [ "a"−le"b" ] < 小于(需要双括号),如:(("a"<"b")) ...
$ echo 'a=8;b=10;if(a==b) print "a equals to b" else print "a not equals to b" ' | bc -l a not equals to b Loops In bc, you can use loop statements to repeat a series of instructions or statements for a certain number of times or until a specific condition is met. Th...
if [condition] then continue fi Commands_to_Execute done Let’s create a Bash while loop that will display numbers 1 to 5 and skip number 2. #!/bin/bash i=0 while [ $i -lt 5 ] do i=$(( $i+1 )) if [ $i -eq 2 ] ...
Another common error is using the wrong operator in the condition. For example, using ‘=’ instead of ‘-eq’ for numerical comparison can lead to unexpected results. a=5b=5# Incorrect syntaxif[$a=$b];thenecho'a is equal to b'fi# Output:# a is equal to b ...
How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if statement? (if not command or if not equal) How to use the BASH_REMATCH variable with the Regular Expression Operator =~?
7 # Same as else if 8 then 9 command4 10 command5 11 else 12 default-command 13 fi使用if test condition-true这种形式和if[condition-true]这种形式是等价的.向我们前边所说的"["是test的标记.并且以"]"结束.在if/test中并不应该这么严厉,但是新版本的Bash需要...