[ILUG] Useless use of cat

[Fergal Daly]

Could it be that your cat behaves differently for you when heading into a 
pipe? I just tried something similar and I get the same result for all 3 
cases: "Binary file (standard input) matches".

Fergal


At 23:31 19/11/00, Niall O Broin wrote:
>One regularly sees here situations where some poor punter is flamed fro what
>the flamer calls useless use of cat e.g. where someone might have said
>
>cat file|some_program
>
>rather than
>
>some_program < file
>
>However, today I came across a necessary, but apparently useless use of cat.
>I had a file with a list of images and some characteristics of those images,
>including their format. I wanted to extract all JPEGs and TIFFs so I
>naturally tried
>
>niall at bagend:/mnt/images :1>egrep "JPEG|TIFF" imagelist.txt
>Binary file imagelist.txt matches
>
>niall at bagend:/mnt/images :2>egrep "JPEG|TIFF" < imagelist.txt
>Binary file (standard input) matches
>
>niall at bagend:/mnt/images :3>cat imagelist.txt | egrep "JPEG|TIFF"
>
>  .
>.
>  .
>lots of output
>  .
>.
>  .
>
>Now a quick perusal of the grep (egrep being of course just grep wearing
>fancy clothes) manual taught me that -a was my friend, but I'm still very
>puzzled by the difference between 2 and 3, when in each case egrep surely
>sees only that it has a non-TTY as its stdin.
>
>
>Regards,
>
>
>Niall
>
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