-bash: syntax error in conditional expression -bash: syntax error near 'string' 可以看到,value变量对应的字符串带有空格,[[ -n $value ]]命令可以正确判断到value变量值不是空字符串,没有对该变量值进行单词拆分。 而test -n $value命令会执行报错,value变量值带有空格,$value经过单词拆分后会变成两个字符...
[root@seker ~]# [[ a = a -a 10 < 20 ]] bash: syntax error in conditional expression -bash: syntax error near `-a' [root@seker ~]# [[ a = a && 10 < 20 ]] [root@seker ~]# echo $? 0 [root@seker ~]# [[ a = a || 10 < 20 ]] [root@seker ~]# echo $? 0 [...
for ip in 192.168.1.{1..255} ;do ping ${ip} -w 1 &> /dev/null && echo ${ip} is Alive;done for ip in `cat iplist`;do scp config/${ip}.conf $ip:/home/shell/;done for x in `cat 1.txt`; do echo $x;mkdir dir{0..2}{0..2}_$x; done for i in `cat iplistr....
$ [[ 1=1]] &&echoTrue bash: conditional binary operator expected bash: syntax error near `True' So, we must pay a little attention when we construct our sentences. 6. Conclusion In this article, we’ve covered conditional expression and how we can build expressions using different constructs...
print"error mark"} } #awk-v mark=100-fif.awkGood 条件表达式 条件表达式(Conditional Expression),也就是我们常见的三目运算符。 selector ?if-true-exp :if-false-exp 三者均是表达式,首先计算selector,若值为真(我们已经在讲解布尔值时解释过awk的真和假的概念了)则计算表达式if-true-exp,并将其返回值...
-bash: syntax error in conditional expression -bash: syntax error near 'on' 可以看到,将value变量值设成空,[[ -n $value ]]返回为 1,确认该变量值不为空是 false。 [[ -z $value ]]返回为 0,确认该变量值为空是 true。 即使$value不加双引号,也能正确判断。
It receives events and, based on those events, runs jobs that can in turn produce more events, causing Upstart to run more jobs, and so on. systemd是目标导向的。你定义一个目标,以及它的依赖关系和你想要达到目标的时间。systemd满足依赖关系并解决目标。systemd还可以推迟启动服务,直到绝对需要时再...
Place the jobs identified by each JOB_SPEC in the background, as if they had been started with `&'. If JOB_SPEC is not present, the shell's notion of the current job is used. Exit Status: Returns success unless job control is not enabled or an error occurs. ...
It would be a good idea to include the system error text from strerror, perror, or equivalent error handling functions, in error messages that result from a crashed on system call, adding the name of the source code file, and also the name of the utility. This is done to make sure ...
官方文档是这么介绍的:The IAR Assembler for Arm is a powerful relocating macro assembler with a versatile set of directives and expression operators. The assembler features a built-in C language preprocessor and supports conditional assembly. 大意就是:IAR Assembler for Arm 是一个功能强大的重定位宏...