Lock

Home › File I/O Functions › Lock

Lock

Restricts other programs' access to a record or byte range of an open file.

Syntax

Lock #filenum, record
Lock #filenum, start To end

Parameters

• filenum
• record
• start
• end

Description

Lock temporarily restricts access by other threads or programs to a file, or portion of a file, usually to allow safe writing to it.

After modifying the data, an Unlock with the same parameters as the Lock should be issued.

Note: This command does not always work, neither as documented nor as expected. It appears to be broken at the moment.

Remarks

Differences from QB

• Currently, FB cannot implicitly lock the entire file
• In Random mode, FB cannot lock a range of records

See also

• Open
• Unlock
• ScreenLock

Examples

'' e.g. locking a file, reading 100 bytes, and unlocking it.

'' To run, make sure there exists a file called 'file.ext'

'' in the current directory that is at least 100 bytes.

Dim array(1 To 100) As Integer

Dim f As Integer, i As Integer

f = FreeFile

Open "file.ext" For Binary As #f

Lock #f, 1 To 100

For i = 1 To 100

    Get #f, i, array(i)

Next

Unlock #f, 1 To 100

Close #f

---

Category: File I/O Functions
Kind: keyword

---

Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.