I/O formatting read data from a previous record

[h_amini]

Hi there

Is it possible to read data from a previous line?

For example my program needs to read the third line (30000) first, then the first line (10000) of the following data file:

01.txt:

10000

20000

30000

I can do it by closing and reopening the data file, but there may be a faster solution, e.g. a command for reading data from a specific line number.

INTEGER A,N

OPEN(unit = 1, file = '01.txt')

n = 2

READ (1,11)A

PRINT*, A

CLOSE(unit = 1)

OPEN(unit = 1, file = '01.txt')

n = 1

READ (1,11)A

PRINT*, A

CLOSE(unit = 1)

11 FORMAT(/,I<5>)

end

Any comment would be very much appreciated.

Regards

Hamid

[Les_Neilson]

Look at BACKSPACE for getting the previous record,
and REWIND to go back to the begining of the file without needing to close and re-open it.

Les

[h_amini]

Quoting - Les Neilson

Look at BACKSPACE for getting the previous record,
and REWIND to go back to the begining of the file without needing to close and re-open it.

Les

Many thanks.

[jimdempseyatthecove]

Also consider

A2 = A1
A1 = A
READ(fmt) A


Then when A is your trigger (30000 in example) use A2

Use an array of prior results when the go-back is larger than a few.

Jim

[bmchenry]

i would suggest tryinginternal reads into a character array and then simply setting the counter back 2 when special situations are encounteredto read prior records.
depending on how large your input dataset is, and how many times you need to check a prior value, you can save valuable time by simply inputting input in arrays (groups of 3) or more?
whenever you doing multiple open/close/rewind you are slowing things down.
memory is cheap and fast there's lots of it out there.

brian