type"$foobar_command_name"> /dev/null;then# install foobar here,or poping up some warning messagesfi references: http://stackoverflow.com/questions/7522712/how-to-check-if-command-exists-in-a-shell-script http://stackoverflow.com/questions/592620/how-to-check-if-a-program-exists-from-a-bash-script
How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if sta...
echo "File does not exists" fi 1. 2. 3. 4. 5. 6. 7. Similarly for example we can use while loop to check if file does not exists. This script will sleep until file does exists. Note bash negator "!" which negates the -e option. #!/bin/bash while [ ! -e myfile ]; do ...
To delete an existing file, you can use anifstatement to check if the file exists and instruct the bash script to remove it. Start by creating the bash script file: nano deletefiles.sh The following script will create a new file namedcars.txt, and then – with the help of the if sta...
-ne 不等于,如:if [ "a"−ne"b" ] -gt 大于,如:if [ "a"−gt"b" ] -ge 大于等于,如:if [ "a"−ge"b" ] -lt 小于,如:if [ "a"−lt"b" ] -le 小于等于,如:if [ "a"−le"b" ] < 小于(需要双括号),如:(("a"<"b")) ...
echo -n "Checking if application exists... "$ if [ -d "/Applications/Install OS X Yosemite.app" ] $ then$ echo "Application is already downloaded and ready to continue."$ sleep 4$ break$ elif [ -f "$script_dir\Yosemite.tar.gz" ]$ ...
This is the job of the test command, which can check if a file exists and its type. Since only the check is completed, the test command sets the exit code to 0 or 1 (either false or true, respectively) whether the test is successful or not. The test command also has a logical "...
Linux test command information and examples (computerhope.com) test/[ ]基本情况 ‘test’: Check file types and compare values man test(获取帮助) test的判断表达式分为4类 string integer expression file testexits with the status determined by EXPRESSION. ...
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 ...
Here, we will list some helping testing operators for permissions, size, date, file type, or existence in the bash script. Operators Explanation -e To test if a file exists. -f To test if a given file is a regular file. -d To test if the file is a directory. -b To test if the...