When you are working on a shell script inbash, there are cases where you want to check if a particular file exists (or does not exist) in a directory, and then perform an action based on the condition. Inbash,
When writing Shell scripts, you may find yourself in a situation where you need to perform an action based on whether a file exists or not. In Bash, you can use the test command to check whether a file exists and determine the type of the file....
In some cases, you may be interested in checking if a file exists or not directly in your Bash shell. In order to check if a file exists in Bash using shorter forms, specify the “-f” option in brackets and append the command that you want to run if it succeeds. [[ -f <file> ...
How to check if a variable exists or is “null”? How to check if a file exists? 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?
Bash: how to check if a process id (PID) exists http://stackoverflow.com/questions/3043978/bash-how-to-check-if-a-process-id-pid-exists https://bugzilla.redhat.com/show_bug.cgi?id=835838
Bash: how to check if a process id (PID) exists,http://stackoverflow.com/questions/3043978/bash-how-to-check-if-a-process-id-pid-existshttps://bugzilla.redhat.com/show_bug.cgi?id=835838
In this case, you probably tried to create a file that already exists. This is common when you try to create a directory with the same name as a file. 在这种情况下,您可能尝试创建一个已经存在的文件。当您尝试以与文件同名的方式创建一个目录时,这种情况很常见。
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Checking if a variable exists ([[ -v varname ]]): Yes, this is possibly a killer argument, but consider the programming style of always setting variables, so you don't need to check if they exist.Are empty string comparisons any special?Of...
be of marginal use, and Section 6 would be great if only it were a little larger. You probably won’t be able to use Section 3 if you aren’t a programmer, but you may be able to understand some of the material in Section 2 once you’ve read more about system calls in this ...