# Read or write a file backwards

**URL:** <https://community.freefem.org/t/read-or-write-a-file-backwards/2522>\
**Category:** General Discussion\
**Created:** [June 6, 2023, 12:10pm UTC](https://community.freefem.org/t/read-or-write-a-file-backwards/2522 "2023-06-06T12:10:09Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![lassounon](https://avatars.discourse-cdn.com/v4/letter/l/bbe5ce/32.png) [@lassounon](https://community.freefem.org/u/lassounon)\
**Post date:** [June 6, 2023, 12:10pm UTC](https://community.freefem.org/t/read-or-write-a-file-backwards/2522/1 "2023-06-06T12:10:09Z")

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Hello everyone.  
I saved a “u” file where u is the solution of an evolution equation in the form: x.y.u(x,y) at each iteration of time t of t=0, x.y.u(x,y)… at t=1, x.y.u(x,y). I would like to know how to create another file whose elements are: t=1, x.y.u(x,y)… to t=0, x.y.u(x,y). That is to reverse the order of the elements of “u”.