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Re: Linux-like touch command in IDL [message #90232 is a reply to message #90223]

Thu, 12 February 2015 13:14

Matthew Argall
Messages: 286
Registered: October 2011

Senior Member

> Does /APPEND solve this?

No, adding /APPEND does not change [ACM]TIME (see below). The following also do not change [ACM]TIME.

File_Move, path, path, /ALLOW_SAME
File_Copy, path, path, /ALLOW_SAME

OpenR, lun, filename, /GET_LUN
free_lun, lun

I thought at least the last operation would change ATIME, but it doesn't. On the otherhand, the following changes ATIME

nLines = File_Lines(path)

So, I thought I maybe the file pointer needed to be moved, but this did not change ATIME either

openr, lun, path, /GET_LUN
point_lun, lun, 1
free_lun, lun

Finally, I tried reading on byte of data, which did change ATIME.

var = 0B
openr, lun, path, /GET_LUN
readu, lun, var

Below is an updated version of touch.pro. Since the same technique does not work with directories, I am left with creating a temporary file and deleting it. This changes all three of [ACM]TIME.

---------------------------------------------

pro touch, path
on_error, 2

;Directory -- Updates access, status change, and modified times.
if file_test(path, /DIRECTORY, /WRITE) then begin
temp_file = filepath('touch_temp_file.txt', ROOT_DIR=path)
openw, lun, temp_file, /GET_LUN
free_lun, lun
file_delete, temp_file

;File -- updates access time
endif else if file_test(path, /READ) then begin
var = 0B
openr, lun, path, /GET_LUN
readu, lun, var

;Other
endif else begin
message, 'PATH must be a file with read privileges or a directory with write privileges.'
endelse
end

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[Message index]

		Linux-like touch command in IDL By: PMan on Sat, 07 February 2015 11:33
		Re: Linux-like touch command in IDL By: Jim Pendleton on Sat, 07 February 2015 14:05
		Re: Linux-like touch command in IDL By: PMan on Tue, 10 February 2015 19:02
		Re: Linux-like touch command in IDL By: Matthew Argall on Thu, 12 February 2015 06:51
		Re: Linux-like touch command in IDL By: Matthew Argall on Thu, 12 February 2015 07:09
		Re: Linux-like touch command in IDL By: Heinz Stege on Thu, 12 February 2015 08:32
		Re: Linux-like touch command in IDL By: Lajos Foldy on Thu, 12 February 2015 08:50
		Re: Linux-like touch command in IDL By: Matthew Argall on Thu, 12 February 2015 13:14
		Re: Linux-like touch command in IDL By: Matthew Argall on Thu, 12 February 2015 13:17
		Re: Linux-like touch command in IDL By: Matthew Argall on Thu, 12 February 2015 13:49
		Re: Linux-like touch command in IDL By: Matthew Argall on Thu, 12 February 2015 12:37

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