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read command - using output from command substitution
Post 302453288 by ProGrammar on Tuesday 14th of September 2010 05:32:40 PM
09-14-2010
read command - using output from command substitution
Hey, guys!
Trying to research this is such a pain since the read command itself is a common word. Try searching "unix OR linux read command examples" or using the command substitution keyword.
So, I wanted to use a command statement similar to the following.
This is kinda taken from another question I posted recently about string manipulation and extracting portions of a string (in order to store to variable, via command substitution).
$ TEMPFILE=`ls -1 *31AUG2010.txt`
yields $TEMPFILE=filetransfers_31AUG2010.txt
$ read DD MM YY<enter>
> `echo ${TEMPFILE:14:2}` `echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`<enter>
which yields:
$DD=`echo
$MM=${TEMPFILE:14:2}`
$YY=`echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`
As you can see, I had intended for each variable to store the output from each command substitution set, but instead stored the literal values between each space encountered on the following input lines. BOOOOO!!
I don't even know if what I'm attempting to do is possible, I wanted to do this in a for loop, storing a new corresponding value for each variable per command set iteration.
Anybody have any experience with this, or how to get command substitution output to work with the read command?
I know that I could just do the command substitution independently for each variable in the loop, but now I'm just curious to know if it's possible to accomplish in one line using the read command.
This is just for my curiosity, but I'd appreciate if somebody could educate me on this matter.
Trying to research this is such a pain since the read command itself is a common word. Try searching "unix OR linux read command examples" or using the command substitution keyword.
So, I wanted to use a command statement similar to the following.
This is kinda taken from another question I posted recently about string manipulation and extracting portions of a string (in order to store to variable, via command substitution).
$ TEMPFILE=`ls -1 *31AUG2010.txt`
yields $TEMPFILE=filetransfers_31AUG2010.txt
$ read DD MM YY<enter>
> `echo ${TEMPFILE:14:2}` `echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`<enter>
which yields:
$DD=`echo
$MM=${TEMPFILE:14:2}`
$YY=`echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`
As you can see, I had intended for each variable to store the output from each command substitution set, but instead stored the literal values between each space encountered on the following input lines. BOOOOO!!
I don't even know if what I'm attempting to do is possible, I wanted to do this in a for loop, storing a new corresponding value for each variable per command set iteration.
Anybody have any experience with this, or how to get command substitution output to work with the read command?
I know that I could just do the command substitution independently for each variable in the loop, but now I'm just curious to know if it's possible to accomplish in one line using the read command.
This is just for my curiosity, but I'd appreciate if somebody could educate me on this matter.
Last edited by ProGrammar; 09-14-2010 at 06:34 PM.. Reason: elaboration, clarification
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tempfile
TEMPFILE(1) General Commands Manual TEMPFILE(1) NAME
tempfile - create a temporary file in a safe manner SYNOPSIS
tempfile [-d DIR] [-p STRING] [-s STRING] [-m MODE] [-n FILE] [--directory=DIR] [--prefix=STRING] [--suffix=STRING] [--mode=MODE] [--name=FILE] [--help] [--version] DESCRIPTION
tempfile creates a temporary file in a safe manner. It uses tempnam(3) to choose the name and opens it with O_RDWR | O_CREAT | O_EXCL. The filename is printed on standard output. See tempnam(3) for the actual steps involved in directory selection. The directory in which to create the file might be searched for in this order (but refer to tempnam(3) for authoritative answers): a) In case the environment variable TMPDIR exists and contains the name of an appropriate directory, that is used. b) Otherwise, if the --directory argument is specified and appropriate, it is used. c) Otherwise, P_tmpdir (as defined in <stdio.h>) is used when appropriate. d) Finally an implementation-defined directory (/tmp) may be used. OPTIONS
-d, --directory DIR Place the file in DIR. -m, --mode MODE Open the file with MODE instead of 0600. -n, --name FILE Use FILE for the name instead of tempnam(3). The options -d, -p, and -s are ignored if this option is given. -p, --prefix STRING Use up to five letters of STRING to generate the name. -s, --suffix STRING Generate the file with STRING as the suffix. --help Print a usage message on standard output and exit successfully. --version Print version information on standard output and exit successfully. RETURN VALUES
An exit status of 0 means the temporary file was created successfully. Any other exit status indicates an error. BUGS
Exclusive creation is not guaranteed when creating files on NFS partitions. tempfile cannot make temporary directories. tempfile is dep- recated; you should use mktemp(1) instead. EXAMPLE
#!/bin/sh #[...] t=$(tempfile) || exit trap "rm -f -- '$t'" EXIT #[...] rm -f -- "$t" trap - EXIT exit SEE ALSO
tempnam(3), mktemp(1) Debian 27 Jun 2012 TEMPFILE(1)