Which command is used to set restrictions on the size of a core file that is created for a user when a program crashes?

`core` is not a standard Linux command for setting resource limits; it typically refers to the core file itself.

`edquota` is used to edit user and group disk quotas, which limits disk space usage, not core file size.

The `ulimit -c` command specifically controls the maximum size of a core file that can be created by a process. Core files are dumps of a process's memory space at the time of a crash, and limiting their size helps manage disk space and security. By setting this limit, administrators or users can prevent excessively large core files from consuming system resources or restrict core file generation entirely.

`quota` is used to display disk usage and quotas, not to set core file size limits.