检查您的拼写 empty ,但也试试这个: #!/bin/bash -e if [ -s diff.txt ]; then # The file is not-empty. rm -f empty.txt touch full.txt else # The file is empty. rm -f full.txt touch empty.txt fi 我非常喜欢 shell 脚本,但它的一个缺点是当你拼写错误时 shell 无法帮助你,而像 ...
-n abc : The string length is not 0 abc : The string is not empty 文件测试运算符 实例: #!/bin/bash file="/home/shiyanlou/test.sh" if [ -r $file ] then echo "The file is readable" else echo "The file is not readable" fi if [ -e $file ] then echo "File exists" else ec...
...以下是使用条件语句检查列是否为空的方法:使用IF语句检查列是否为空:SELECT column_name, IF(column_name IS NULL, 'Empty', 'Not Empty') AS...使用聚合函数检查列是否为空聚合函数也可以用于检查列是否为空。例如,我们可以使用COUNT函数统计为空的行数来判断列是否为空。...我们还提供了案例研究,展示...
echo'~/.bash_profile is a file'elseecho'~/.bash_profile is not a file'fi printf'\n'if[-d~/];then echo'~/ is a directory'elseecho'~/ is not a directory'fi -f即判断是否为file, -d即判断是否为directory, 输出结果: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 +'['-f/Users...
filename=ttt.shif[ -e"$filename"];then# 注意: "if"和"then"需要分隔,-e用于判断文件是否存在echo"File$filenameexists.";cp$filename$filename.bakelseecho"File$filenamenot found.";touch$filenamefi;echo"File test complete." 双分号;;
After running this Bash code, we have got “Empty” as the variable “v” is empty. $ bash ifnot.sh Example 4 Within our last example, we will be checking whether the simple Bash file is located in the current home directory or other folders or not. For this, we will be using the...
注意到then不放在下一行,与if放在用一行,用;来隔开。 if [ -n "$mystack" ]; then cd ${mystack%% *} echo "$PWD", stack is [$mystack] else echo "stack empty, still in $PWD." fi } 1. 2. 3. 4. 5. 6. 7. 8. 9. 10....
Similarly for example we can use while loop to check if file does not exists. This script will sleep until file does exists. Note bash negator "!" which negates the -e option. #!/bin/bash while [ ! -e myfile ]; do # Sleep until file does exists/is created ...
pushd "$dir" > /dev/null if [ $no_dots -ne 0 ] ; then find . -maxdepth 1 -type $type $find_extras -not -name ".*" -printf "%f\000" \ | xargs --null --no-run-if-empty ls $opts -- ; else find . -maxdepth 1 -type $type $find_extras -printf "%f\000" \ | ...
Check to see if a variable is empty or not Create a new bash file, named, and enter the script below. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. This script will print the first argument because it is not em...