# file

file management

## Calling Sequence

    [unit [,err]]=file('open', file-name [,status] [,access [,recl]] [,format])
                file(action,unit)
                [units [,typ [,nams [,mod [,swap]]]]] = file([unit])

## Arguments

file-name

  string, file name of the file to be opened

status

  string, The status of the file to be opened

  "new"

    file must not exist new file (default)

  "old"

    file must already exists.

  "unknown"

    unknown status

  "scratch"

    file is to be deleted at end of session

access

  string, The type of access to the file

  "sequential"

    sequential access (default)

  "direct"

    direct access.

format

  string,

  "formatted"

    for a formatted file (default)

  "unformatted"

    binary record.

recl

  integer,is the size of records in bytes when `access="direct"`

unit

  integer, logical unit descriptor of the opened file

units

  integer vector, logical unit descriptor of the opened files. Units 5 and 6 (%io) are reserved by the system for input and output devices.

typs

  Character string vector, type (C or Fortran) of opened files.

nams

  Character string vector, pathnames of opened files.

mod

  file opening mode. Formed by three digits abc

  Fortran files
    a

      0 stands for formatted and 1 for unformatted (binary)

    b

      0 stands for sequential access and 1 for direct access

    c

      0 stands for "new", 1 for "old", 2 for "scratch" and 3 for "unknown"

  C files
    a

      1 stands for "r" (read), 2 stands for "w" (write) and 3 for "a" (append)

    b

      is 1 if file has been opened with a "+" (updating) mode

    b

      is 1 if file has been opened with a "b" (binary) mode

swap

  automatic swap switch. swap=1 if automatic swap is on. swap is always 0 for Fortran files.

err

  integer, error message number (see error), if open fails. If err is omitted an error message is issued.

action

  is one of the following strings:

  "close"

    closes the file(s) given by the logical unit descriptors given in `units`

  "rewind"

    puts the pointer at beginning of file

  "backspace"

    puts the pointer at beginning of last record.

  "last"

    puts the pointer after last record.

## Description

selects a logical unit `unit` and manages the file `file-name`.

`[unit [,err]]=file('open', file-name [,status] [,access [,recl]][,format])` allows to open a file with specified properties and to get the associated unit number `unit`. This unit number may be used for further actions on this file or as file descriptor in `read`, `write`, `readb`, `writb`,`save`, `load` function calls.

This function can not open a UTF filename. In this case, please uses mopen.

`file(action,unit)` allows to close the file , or move the current file pointer .

`file()` returns the logical unit descriptors of the opened files. So `file('close',file() )` closes all user opened files (C or Fortran type).

## Examples

    u=file('open',TMPDIR+'/foo','unknown')
    for k=1:4
      a=rand(1,4)
      write(u,a)
    end
    file('rewind',u)
    x=read(u,2,4)
    file('close',u)
    //
    u1=file('open',TMPDIR+'/foo','unknown')
    u2=mopen(TMPDIR+'/foo1','wb')
    [units,typs,nams]=file()
    file('close',u1);
    mclose(u2);

## See Also

- save
- load
- write
- read
- writb
- readb
- uigetfile
- mopen
- mclose
- file