About “bash if file does not exist” issue You might want to check if file does not exist in bash in order to make the file manipulation process easier and more streamlined. This is the job of the test command,
# Check if a file exists if [ -f $file ] then echo "File exists" else echo "File does not exist" fi # Check if a command is successful if ls then echo "Command succeeded" else echo "Command failed" fi ``` 通过使用if-else语句,用户可以根据不同的条件执行不同的操作。这使得Bash脚本...
在Bash Shell中,可以使用复合条件来在一个if语句中检查多个条件。复合条件主要有两种形式:逻辑与(&&)和逻辑或(||)。 1. 逻辑与(&&): - 概念:逻辑与用于同时检查多个条件...
if TEST-COMMANDS; then CONSEQUENT-COMMANDS; fi TEST-COMMAND 执行后且它的返回状态是0,那么 CONSEQUENT-COMMANDS 就执行。返回状态是最后一个命令的退出状态,或者当没有条件是真的话为0。 TEST-COMMAND 经常包括数字和字符串的比较测试,但是也可以是任何在成功时返回状态0或者失败时返回一些其他状态的一些命令。一...
11. Bash File Testing #!/bin/bash file="./file" if [ -e $file ]; then echo "File exists" else echo "File does not exists" fi 1. 2. 3. 4. 5. 6. 7. Similarly for example we can use while loop to check if file does not exists. This script will sleep until file does exi...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
== 等于,如:if [ "a"=="b" ],与=等价 注意:==的功能在[[]]和[]中的行为是不同的,如下: [[ a == z* ]] # 如果a以"z"开头(模式匹配)那么将为true [[ a == "z*" ]] # 如果a等于z*(字符匹配),那么结果为true [ a == z* ] # File globbing 和word splitting将会发生 [ "a" ...
Now let’s perform a similar check,but with thetest [command: $ if [ -x a.out ]; then echo "File is executable"; else echo "File is not executable"; fi File is executable So, thetest‘sxflag proves if the file exists and is executable. ...
/Users/will/Desktop/yosemite.sh:line3:echo-e ### CreatingOSXYosemiteISO###\n:command not found 在下面,我将工作命令放在非工作命令下面(注释掉的那个命令),它们看起来是一样的。当然,只有最下面的一个起作用。好像某个地方有个无效的角色。现在,如果我有时间,我会从头开始写整件事,但这是完全没有效率...
Check if string contains a sub-stringUsing a test:if [[ $var == *sub_string* ]]; then printf '%s\n' "sub_string is in var." fi # Inverse (substring not in string). if [[ $var != *sub_string* ]]; then printf '%s\n' "sub_string is not in var." fi # This works ...