-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 $file ] then echo "File exists" else ec...
...以下是使用条件语句检查列是否为空的方法:使用IF语句检查列是否为空:SELECT column_name, IF(column_name IS NULL, 'Empty', 'Not Empty') AS...使用聚合函数检查列是否为空聚合函数也可以用于检查列是否为空。例如,我们可以使用COUNT函数统计为空的行数来判断列是否为空。...我们还提供了案例研究,展示...
folder="log"if[ ! -d"${folder}"]; then mkdir ${folder} fi2、判断文件是否存在 file="/var/www/log.txt"#-f 参数判断 $file 是否存在if[ ! -f"$file"]; then touch"$file"fi、3、# -n 判断一个变量是否有值if[ ! -n"$var"]; then echo"$var is empty"exit0f4# 判断两个变量是否...
参数可以是以下任意一种:-e: Returns true value, if file exists-f: Return true value, if file exists and regular file-r: Return true value, if file exists and is readable-w: Return true value, if file exists and is writable-x: Return true value, if file exists and is executable-d: ...
Check to see if a variable is empty or not Create a new bash file, named, and enter the script below. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. This script will print the first argument because it is not em...
filename="bashfile.sh" size_threshold=1 # Check if file exists if[-e"$filename"] then # Get file size in bytes file_size=$(wc-c<"$filename") # Check if file is empty if["$file_size"-gt"$size_threshold"] then echo"File exists and is not empty" ...
/bin/sh if [ -s java 判断目录是否为空的方法 linux判断空目录的函数 逻辑值 文件名 当前目录 转载 技术领航探索者 2023-12-07 17:31:37 114阅读 mfc判断目录是否为空 BOOL IsFolderEmpty(string path) { string str = path + "\\*.*"; CFileFind ff; BOOL bFound; bFound = ff.FindFile(str....
if [[ -z $string ]]; then echo "The string is empty." else echo "The string is not empty." fi 这是我们执行脚本时的结果: 代码语言:txt AI代码解释 $ ./test.sh Strings are different. 例4 -n运算符还可用于测试字符串长度是否不为零。
echo "$a : The string is not empty" else echo "$a : The string is empty" fi 1. 2. 3. 4. 5. 6. 7. 8. 文件比较运算符 如下例: #!/bin/bash file="/test.sh" # 由于没有给出条件,所以返回true if [ ! ] then echo "File exists" ...
-e FILE_NAM # True if FILE_NAM exists -f FILE_NAM # True if FILE_NAM exists and is a regular file -r FILE_NAM # True if FILE_NAM is readable -s FILE_NAM # True if FILE_NAM exists and is not empty -w FILE_NAM # True if FILE_NAM has write permission ...