# 双括号在 for 循环中的使用 for (( i = 0; i < 5; i++)); do echo "循环中${i}"; done # 如何判断空的变量? # 这里会出现一个误区 [ ${emptyvar} = "" ],这个等于 [ = "" ],所以会报错 # 而下面的2个方法都是可行的 emptyvar= if [ "${emptyvar}" = "" ]; then echo "...
而if [ ! -z err]||[!−eapk ]; then 没问题; 整数比较 : -eq 等于,如:if [ "a"−eq"b" ] -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...
function empty { local var="$1" # Return true if: # 1. var is a null string ("" as empty string) # 2. a non set variable is passed # 3. a declared variable or array but without a value is passed # 4. an empty array is passed if test -z"$var" then [[ $( echo"1" ...
echo $CUR_DIRforvalin$CUR_DIRdo# 若val是文件,则输出该文件名if[-f $val];then echo"FILE: $val"fi done 2.4 循环 For循环基本格式:for variable in list do commands done While语句基本语句格式为:while test-condition do commands done 2.5 ...
/bin/bash # declare STRING variable STRING="Hello World" #print variable on a screen echo $STRING Navigate to a directory where your hello_world.sh is located and make the file executable: $ chmod +x hello_world.sh Now you are ready to execute your first bash script:...
# Check if the variable is empty if [ -z "$variable" ]; then echo "Variable is empty." else echo "Variable is not empty." fi Copy Save changes and exit from the nanotext editor. Finally,use the chmod command to make the file executableas shown: ...
下列詞被識別為保留的, 如果不是引用, 並且不是一個簡單命 令的起始詞 (參見下面的 shell語法("SHELL GRAMMAR") ), 也不是 case 或者for 命令的第三個詞: ! case do done elif else esac fi for function if in select then until while { } time [[ ]] ...
Here, we list some basic bash syntax with a brief explanation. It is a good starting point if you are a beginner.
if test $[num1] -eq $[num2] then echo 'Two numbers are equal!' else echo 'The two numbers are not equal!' fi 1. 2. 3. 4. 5. 6. 7. 8. 循环语句 AI检测代码解析 for loop in 1 2 3 4 5 do echo "The value is: $loop" ...
[student@studentvm1 testdir]$ File="TestFile1" ; touch $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; elif [ -e $File ] ; then echo "$File exists and is empty." ; else echo "$File does not exist." ; fi TestFile1 exists and is empty. [stude...