In the cp or mv commands in bash shell, {,} is used to specify multiple target destinations for the source file(s). It’s a brace expansion feature in bash, which allows you to repeat a command multiple times with different arguments.
For example, if you want to copy a file “file1.txt” to two different directories, you can use the following command:
cp file1.txt dir1/{,}
This command will copy file1.txt to both dir1/ and dir1/file1.txt.
Similarly, if you want to move a file “file2.txt” to two different directories, you can use the following command:
mv file2.txt dir2/{,}
This command will move file2.txt to both dir2/ and dir2/file2.txt.
It’s a convenient and concise way to specify multiple target destinations for a file, without having to repeat the command multiple times.