Checking File Status
System routines that deal with files must verify that the files have the proper attributes for the intended operation. Use the function IDL_FileEnsureStatus() for this.
IDL_FileEnsureStatus()
action
If the file unit does not satisfy the requirements of the flags argument, IDL_FileEnsureStatus() will issue an error using the IDL_Message() function (see Issuing Error Messages). This action is the action argument to IDL_Message() and should be IDL_MSG_RET, IDL_MSG_LONGJMP, or IDL_MSG_IO_LONGJMP.
unit
The Logical Unit Number of the file to be checked.
flags
IDL_FileEnsureStatus() always checks to make sure unit is a valid logical file unit. In addition, flags is a bit mask specifying the file attributes that should be checked. The possible bit values are listed in the following table:
Table 13-5: Bit Values for the flags Argument
|
Bit Value
|
Description
|
|
IDL_EFS_USER
|
The file must be a user unit. This means that the file is not one of the three special files, stdin, stdout, or stderr.
|
|
IDL_EFS_IDL_OPEN
|
The file unit must be open.
|
|
IDL_EFS_CLOSED
|
The file unit must be closed.
|
|
IDL_EFS_READ
|
The file unit must be open for input.
|
|
IDL_EFS_WRITE
|
The file unit must be open for output.
|
|
IDL_EFS_NOTTY
|
The file unit cannot be a tty.
|
|
IDL_EFS_NOGUI
|
The file unit cannot be a Graphical User Interface.
|
|
IDL_EFS_NOPIPE
|
The file unit cannot be a pipe.
|
|
IDL_EFS_NOXDR
|
The file unit cannot be a XDR file.
|
|
IDL_EFS_ASSOC
|
The file unit can be ASSOC'ed. This implies IDL_EFS_USER, IDL_EFS_OPEN, IDL_EFS_NOTTY, IDL_EFS_NOPIPE, IDL_EFS_NOXDR, IDL_EFS_NOCOMPRESS, and IDL_EFS_NOSOCKET.
|
|
IDL_EFS_NOT_RAWIO (formerly called IDL_EFS_NOT_NOSTDIO)
|
The file was not opened with the IDL_F_UNIX_RAWIO attribute. This bit was formerly called IDL_F_NOTSTDIO. IDL_EFS_NOT_RAWIO is the preferred form, but both names are accepted.
|
|
IDL_EFS_NOCOMPRESS
|
The file unit cannot have been opened for compressed input/output (IDL_F_COMPRESS).
|
|
IDL_EFS_STDIO
|
The file must be using the C stdio package (IDL_F_STDIO).
|
|
IDL_EFS_NOSOCKET
|
The file unit cannot be a socket (IDL_F_SOCKET).
|
Note
Some of these values are contradictory. The caller must select a consistent set.
If the file unit meets the desired conditions, IDL_FileEnsureStatus() returns TRUE. If it does not meet the conditions, and action was IDL_MSG_RET, then it returns FALSE.
