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P4 CLI Documentation | 2026.1

# Preventing multiple checkouts

To ensure that only one user at a time can work on the file, use the `+l` (exclusive-open) file type modifier. For example:

    p4 reopen -t binary+l file

Although exclusive locking prevents concurrent development, for some file types (binary files), merging and resolving are not meaningful, so you can prevent conflicts by preventing multiple users from working on the file simultaneously.

Your P4 Server administrator can use the `p4 typemap` command to ensure that all files of a specified type (for instance, `//depot/.../*.gif` for all `.gif` files) can only be opened by one user at a time. To learn more, see `p4 typemap`.

The difference between `p4 lock` and `+l` is that `p4 lock` allows anyone to open a file for edit, but only the person who locked the file can submit it. By contrast, a file of type `+l` prevents more than one user from opening the file.

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