On major systems, “[“ is offered as an executable, and to check if your system has any such executable, run:which [/usr/bin/[If a path is printed on the terminal, we can also run the following, which prints the help section of the man page to the terminal....
For example, to test if the file/tmp/test.logexists, run the following command: test -f /tmp/test.txtCopy The first line executes the test to see if the file exists. The second command,echo, displays the results. The result0means that the file exists, while1means no file was found....
But here, we used the which command, which is used to locate the executable file that would be executed if a command is run. It is also used to determine if the specified command exists. In the above code, the if statement checks if the wget command exists by running the command which...
-t fd True if file descriptor fd is open and refers to a terminal. -u file True if file exists and its set-user-id bit is set. -w file True if file exists and is writable. -x file True if file exists and is executable.
-xIt is used to check if the file exists as an executable file. -sIt is used to check if the file exists and if the file is nonzero. -bIt is used to check if the file exists as a block special file. -cIt is used to check if the file exists as a special character file. ...
The “||” operator will execute the command on the right if and only if the command on the left fails (i.e exits with a status greater than zero). To test if a file does not exist using the “||” operator, simply check if it exists using the “-f” flag and specify the comm...
Thesebinarylogical expressions compare two values, but there are alsounarylogical expressions that only look at one value. For example, you can test whether or not a file exists using the-elogical flag. Let’s take a look at this flag in action: ...
is readable-s FILE_NAM # TrueifFILE_NAM existsandisnotempty-w FILE_NAM # TrueifFILE_NAM has write permission-x FILE_NAM # TrueifFILE_NAM is executable#字符串测试操作-z STRING # TrueifSTRING is empty-n STRING # TrueifSTRING isnotemptySTRING1...
Navigate to a directory where your hello_world.sh is located and make the file executable: $ chmod +x hello_world.sh Now you are ready to execute your first bash script: ./hello_world.sh 2. Simple Backup bash shell script #!/bin/bash tar -czf myhome_directory.tar.gz /home/linuxconf...
Check if file does not exists if [ ! -f /tmp/users.txt ]; then echo "File not found" fi Parameterize file name in script to check if file doesn’t exist filecheck.sh #!/bin/bash FILEPATH=$1 if [ ! -f "$FILEPATH" ]; then ...