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Top Forums UNIX for Dummies Questions & Answers Redirection of file input to command Post 302856179 by wisecracker on Monday 23rd of September 2013 09:28:27 AM
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~> _

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echo(1B)					     SunOS/BSD Compatibility Package Commands						  echo(1B)

NAME
echo - echo arguments to standard output SYNOPSIS
/usr/ucb/echo [-n] [argument] DESCRIPTION
echo writes its arguments, separated by BLANKs and terminated by a NEWLINE, to the standard output. echo is useful for producing diagnostics in command files and for sending known data into a pipe, and for displaying the contents of envi- ronment variables. For example, you can use echo to determine how many subdirectories below the root directory (/) is your current directory, as follows: o echo your current-working-directory's full pathname o pipe the output through tr to translate the path's embedded slash-characters into space-characters o pipe that output through wc -w for a count of the names in your path. example% /usr/bin/echo "echo $PWD | tr '/' ' ' | wc -w" See tr(1) and wc(1) for their functionality. The shells csh(1), ksh(1), and sh(1), each have an echo built-in command, which, by default, will have precedence, and will be invoked if the user calls echo without a full pathname. /usr/ucb/echo and csh's echo() have an -n option, but do not understand back-slashed escape characters. sh's echo(), ksh's echo(), and /usr/bin/echo, on the other hand, understand the black-slashed escape characters, and ksh's echo() also understands a as the audible bell character; however, these commands do not have an -n option. OPTIONS
-n Do not add the NEWLINE to the output. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWscpu | +-----------------------------+-----------------------------+ SEE ALSO
csh(1), echo(1), ksh(1), sh(1), tr(1), wc(1), attributes(5) NOTES
The -n option is a transition aid for BSD applications, and may not be supported in future releases. SunOS 5.11 3 Aug 1994 echo(1B)
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