DB_ENV->set_thread_id_string()
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## DB_ENV->set_thread_id_string()

    #include <db.h>

    int
    DB_ENV->set_thread_id_string(DB_ENV *dbenv,
        char *(*thread_id_string)(DB_ENV *dbenv,
        pid_t pid, db_threadid_t tid, char *buf));

Declare a function that formats a process ID and thread ID identifier pair for display into a caller-supplied buffer. The function must return a reference to the caller-specified buffer. The `DB_ENV->set_thread_id_string()` method supports the DB_ENV->set_thread_id() method.

The `DB_ENV->set_thread_id_string()` method configures operations performed using the specified DB_ENV handle, not all operations performed on the underlying database environment.

The `DB_ENV->set_thread_id_string()` method may be called at any time during the life of the application.

The `DB_ENV->set_thread_id_string()` method returns a non-zero error value on failure and 0 on success.

### Parameters

#### thread_id_string

The thread_id_string parameter is a function which returns a buffer in which is an identifier pair formatted for display. The function takes four arguments:

- `dbenv`

  The dbenv parameter is the enclosing database environment handle, allowing application access to the application-private fields of that object.

- `pid`

  The pid argument is a process ID.

- `tid`

  The tid argument is a thread ID.

- `buf`

  The buf argument is character array of at least DB_THREADID_STRLEN bytes in length, into which the identifier pair should be formatted.

If no thread_id_string function is specified, the default routine displays the identifier pair as "pid/tid", that is, the process ID represented as an unsigned integer value, a slash ('/') character, then the thread ID represented as an unsigned integer value.

### Errors

The `DB_ENV->set_thread_id_string()` method may fail and return one of the following non-zero errors:

#### EINVAL

An invalid flag value or parameter was specified.

### Class

DB_ENV

### See Also

Database Environments and Related Methods

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