# System Functions

FID( ) | Return File Information Descriptor

## Format

FID(chan[,ERR=stmtref])
Where:

chan | Channel or logical file number of the file to return information about.
stmtref | Program line number or statement label to which to transfer control.

## Returns

String, file information descriptor.

## Description

The FID( ) function returns a character string containing the file information descriptor for an existing open file. If the file is a device (printer, terminal, etc.), the filename used to open the file will be returned. If the file is a disk file, a file description string is returned. You can make subsequent use of this file description by passing it to a FILE directive to recreate the file.

See File Information Functions Overview and PxPlus Standard Format for FIB(0) and FID(0).

If you are running PxPlus in an emulation mode, the format of the information returned will be changed to reflect the system being emulated.

#### Note:
When 'FF' is set to 0 or 3 and the 'PO' system parameter is switched On, the FID( ) and FIB( ) function returns the original path used when the file was opened. In addition, the FID( ) and FIN( ) format layouts will be changed whenever there is a change to the 'FF' system parameter.

Determining FID in PxPlus Under UNIX

By default, PxPlus assigns a unique FID value for each terminal based on the /etc/initab entry for the terminal. Unfortunately, when you use dynamic terminal allocation (e.g. Telnet), each time a user signs off and then signs on, he/she will have a different FID value. There are workarounds; however, no one solution works in all instances. If, for security purposes, you use the User_ID rather than the Terminal_ID, you can set the file information descriptor in the user's profile by inserting the following lines:

> PVXFID0=desired_FID_val
> export PVXFID0

As an alternative, you can assign the file information descriptor once in PxPlus by issuing a SETFID directive to establish a new FID(0) value. If you do not want to use User_IDs but you are using Telnet and PCs, see if there is a host-initiated file transfer you could use to get a file containing the FID value off the PC.

Using WindX, you could open a file on the PC and read it to determine a FID value:

> open (1)"[wdx]C:\PVXFID"
> read record (1)F$
> close (1)
> setfid F$

Finally, you could see if the terminal emulator allows you to define values for function keys and has an escape sequence to send the values. Some terminals send a "HEREIS" string on receipt of an ENQ (Hex $05$); however, this varies from terminal to terminal.

FIB(1) / FID(1)'FF'=1

Bytes | Description (Total Length = 22 bytes)
1,3 | $000000$
4,6 | Characters 1 - 6 of filename
10,1 | File type indicator: $00$ Indexed $01$ Serial - WindX connected file (any type) $02$ Keyed or EFF $03$ Open via ISZ= (binary) $04$ Program $06$ ZIP $0D$ Directory $0F$ Device
11,1 | External key size
12,3 | Maximum number of records
15,2 | Record size
17,4 | Reserved for future use
21,2 | Characters 7 - 8 of filename

FIB(2) / FID(2)'FF'=2

Bytes | Description (Total Length = 16 bytes)
1,6 | Characters 1 - 6 of filename
7,1 | File type indicator: $00$ Indexed $01$ Serial - WindX connected file (any type) $02$ Keyed $03$ Open via ISZ= (binary) $04$ Program $06$ ZIP $0D$ Directory $0F$ Device
8,1 | External key size
9,2 | Maximum number of records (bytes reversed)
11,2 | Record size (bytes reversed)
13,4 | Not Used

FIB(3) / FID(3)'FF'=3

Bytes | Description (Total Length = 9+ bytes)
1,1 | File type indicator: $00$ Indexed $01$ Sequential - WindX connected file (any type) $02$ Keyed $03$ Opened via ISZ= (binary) $04$ Program $05$ Directory $06$ BBxMkeyed (no external key) or $06$ ZIP $07$ C-Isam $0A$ UNIX Pipe $0E$ TCP/IP-Network $0F$ Device/Attached Printer
2,1 | External key size
3,4 | Maximum number of records
7,2 | Record size (bytes reversed)
9,... | Pathname Example: set_param 'FF'=3 open (30)"SESAME" A$=fid(30) print A$(9) run C:\OTHER\TESTS\SESAME
1,... | Device name Example: set_param 'FF'=3 open (31)PRINTER$ B$=fid(31); print B$ ->run LPT1 [Details for files, above (1,1 to 9,...) inapplicable]

FIB(4) / FID(4)'FF'=4

FID(4) is the same as FID(3); however, all serial files return a file type indicator of $03$ for binary. This format is only intended to facilitate program migration to PxPlus.

## See Also

FIB( ) Return File Information Block
FIN( ) Return File Information
FILE Create New File from File Descriptor
'FF' File Format
'PO' Path Original