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Redirection of file input to command

 
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# 1  
Old 09-23-2013
Redirection of file input to command
Hello,

I'm new to Unix (working with OS X 10.8.5) and therefore at the beginning of my adventure. If I ask something stupid, then this is not intentional, but simple nescience. Smilie

I have a problem with the redirection of text file content to echo. I was experimenting with redirection and stuff like that and I think I borked something.

I think this commands worked for my in the bash but I'm not sure anymore:
Code:
echo < file.txt

I expect that this will force echo to print the text file content to the command line. But this is not happen. Nothing but a newline is printed. Maybe my memories are wrong and this never worked. As I said, I'm not sure anymore.

I created this file with the following command:
Code:
ls -l > file.txt

And this is working. The file exists. But not the other direction.

What is at this moment wrong? My memories or my file descriptors?
# 2  
Old 09-23-2013
A starter for you:-

OSX 10.7.5, default bash terminal done longhand...
Code:
Last login: Mon Sep 23 09:11:17 on console
AMIGA:barrywalker~> text="This is a line."
AMIGA:barrywalker~> echo -n "$text" > /tmp/txt
AMIGA:barrywalker~> read newtext < /tmp/txt
AMIGA:barrywalker~> echo "$newtext"
This is a line.
AMIGA:barrywalker~> _

This User Gave Thanks to wisecracker For This Post:
pseudo
# 3  
Old 09-23-2013
Thank you for your fast answer. Smilie

This means, as I wrote it, it never been able to work? I'm so sure that this was working before.... Smilie

I thought I changed the file descriptors to a state, that's causing this behavior.
# 4  
Old 09-23-2013
Again longhand to demonstrate...
Code:
Last login: Mon Sep 23 14:05:22 on ttys000
AMIGA:barrywalker~> text="This is a line."
AMIGA:barrywalker~> echo -n "$text" > /tmp/txt
AMIGA:barrywalker~> read newtext < /tmp/txt
AMIGA:barrywalker~> echo "$newtext"
This is a line.
AMIGA:barrywalker~> # Use echo direct.
AMIGA:barrywalker~> echo < /tmp/txt

AMIGA:barrywalker~> # Nothing!
AMIGA:barrywalker~> # Now attempt to force into a variable.
AMIGA:barrywalker~> oldtext=$(echo < /tmp/txt)
AMIGA:barrywalker~> # Check "oldtext".
AMIGA:barrywalker~> echo "$oldtext"

AMIGA:barrywalker~> # Again nothing.
AMIGA:barrywalker~> # Now check the variable length.
AMIGA:barrywalker~> echo ${#oldtext}
0
AMIGA:barrywalker~> # As you can see no characters.
AMIGA:barrywalker~> _

This User Gave Thanks to wisecracker For This Post:
pseudo
# 5  
Old 09-23-2013
echo prints its arguments, not its stdin.
You can use xargs to transform stdin to arguments
Code:
xargs -i echo {} < file.txt

or simply
Code:
cat file.txt

This User Gave Thanks to MadeInGermany For This Post:
pseudo
# 6  
Old 09-23-2013
Thanks guys, you've helped me a lot to solve this brainteaser. I hope these are not the first signs of Alzheimer. Smilie
# 7  
Old 09-23-2013
Without trying to be picky, -i of xargs is deprecated. You should use -I instead.

xargs
 
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