possibly to the empty string"fiif [ -n "${JAIL-unset}" ]; then echo "JAIL is either unset or set to a non-empty string"fidone## syntax 1 ##if [[ -z "$variable" ]]; then echo "Empty $variable"else echo "Do whatever you want as ...
empty_string="" if [ $X -lt $Y ]# is $X less than $Y ? then echo "$X=${X}, which is smaller than $Y=${Y}" fi if [ -n "$empty_string" ]; then echo "empty string is non_empty" fi if [ -e "${HOME}/.fvwmrc" ]; then # test to see if ~/.fvwmrc exists echo...
empty_string="" if[ $X -lt $Y ]# is $X less than $Y ? then echo"$X=${X}, which is smaller than $Y=${Y}" fi if[ -n"$empty_string"];then echo"empty string is non_empty" fi if[ -e"${HOME}/.fvwmrc"];then# test to see if ~/.fvwmrc exists echo"you have a .fv...
2. String Comparisons: ==: Equal to !=: Not equal to -z: Empty string -n: Non-empty string 3. File and Directory Checks: -e: Exists -f: Regular file -d: Directory -r: Readable -w: Writable -x: Executable Example of using If Statement: Let’s illustrate the usage of if stateme...
echo "Empty String" fi 非空判断是一样的: if [ -n "$a" ] then echo "Non-empty String" fi 3. 字符串大小的比较 关于这个,我用了五年的shell,居然今天一个同事问到我这个怎么搞的时候不知道怎么搞-_-真是晕菜。差点就告诉他bash不能搞这个了,还好没有丢人后来翻书翻出来了。 网上...
if (s != null && s.isEmpty()) { // do something } 不是null也不是空串:方法三 import org.apache.commons.lang.StringUtils; if (StringUtils.isNotEmpty(s)) { // do something } JavaDoc String.isEmpty 写道 boolean isEmpty() Returns true if, and only if, length() is 0. ...
注意,if [ check_space ]并没有做你认为它做的事情:函数check_space根本不会被调用。check_space只是test([)命令的字符串。[ string ]检查字符串的长度:如果字符串为non-empty,则返回true,否则返回false。 您还可以考虑将路径和大小作为参数传递给函数: ...
$ checkarg /home/chris/bin/checkarg: line 10: 1: An argument is required $ checkarg x /home/chris/bin/checkarg: line 10: 2: Two arguments are required $ checkarg '' '' /home/chris/bin/checkarg: line 13: 1: A non-empty argument is required $ checkarg x '' /home/chris/bin...
string:如果字符串的长度为non-zero,则为True。 string1 == string2:如果字符串相等,则为True。 换句话说,一个比较需要三个元素,这意味着您需要在==的两边都有一个空格。 没有这一点,它只是条件的one-element变量,当字符串为non-empty时,这是真的,正如hello==h最肯定的那样。本...
...>>> a = ” #这里仅以空字符串为例,其他空值同样适用 >>> if a: … print ‘a is not empty’ … else: … print...if a会首先去调用a的__nonzero__()去判断a是否为空,并返回True/False,若一个对象没有定义__nonzero__(),就去调用它的__len__()来进行判断(这里返回值为0代表空...