Shell Bash determines whether a file or folder exists

#shell判断文件夹是否存在 # If the folder does not exist, create a folder if [!-D "/myfolder"]; Then  Mkdir/myfolderfi#shell determine the file, whether the directory exists or has permissions folder= "/var/www/" file= "/var/www/log" #-x parameter to determine $folder Whether it exists and has enforceable permissions if [!-X ' $folder];  Then  mkdir the "$folder" fi#-D parameter to determine if there is an IF [!-D "$folder"]; then  mkdir "$folder" fi#-F parameter to determine if $file exists if [! -F "$file"]; Then  touch "$file" fi#-N to determine if a variable has a value if [!-n "$var"]; then  echo "$var is empty"  exit 0fi# determine if two variables are equal if ["$va R1 "=" $var 2 "]; Then  echo ' $var 1 eq $var 2 ' else  echo ' $var 1 not EQ $var 2 ' fi

Shell Bash determines whether a file or folder exists