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Top Forums UNIX for Dummies Questions & Answers read command - using output from command substitution Post 302453583 by ProGrammar on Wednesday 15th of September 2010 08:25:39 PM
Old 09-15-2010
I was reading that because each segment of a pipeline is handled inna child shell of the parent, that setting multiple variables using output from preceding segments of a pipeline into a read command statement only stores the variables for the read arguments in the subshell, so the values assigned to the variables are not returned to the parent process.

If I pipe the output of a command into `read variable', why doesn't the output show up in $variable when the read command finishes?

I was however able to successfully get read to take the space-delimted output from a command substitution statement, using a Here-Document.

See below.

This was done using bourne shell.

$ read YY MM DD << EOF
> `echo "${TEMPFILE:14:2} ${TEMPFILE:16:3} ${TEMPFILE:19:4}"`
> EOF
$ echo $YY $MM $DD
10 09 06


I hope this helps anybody else trying to accomplish the same thing. It worked as intended...eventually, after several attempts to play with damm I/O redirection with file descriptors and such. WHY CAN'TCHU JUST DO WHAT I WANT, UNIX?! YOU STUPID ROBOT!

~another rant brought to you by your friendly neighborhod programmar
 

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read(1) 						      General Commands Manual							   read(1)

NAME
read - read a line from standard input SYNOPSIS
var ... DESCRIPTION
reads a single line from standard input. The line is split into fields as when processed by the shell (refer to shells in the first field is assigned to the first variable var, the second field to the second variable var, and so forth. If there are more fields than there are specified var operands, the remaining fields and their intervening separators are assigned to the last var. If there are more vars than fields, the remaining vars are set to empty strings. The setting of variables specified by the var operands affect the current shell execution environment. Standard input to can be redirected from a text file. Since affects the current shell execution environment, it is usually provided as a normal shell special (built-in) command. Thus, if it is called in a subshell or separate utility execution environment similar to the following, it does not affect the shell variables in the caller's environment: Options recognizes the following options: Do not treat a backslash character in any special way. Consider each backslash to be part of the input line. Opperands recognizes the following operands: var The name of an existing or nonexisting shell variable. EXTERNAL INFLUENCES
Environment Variables determines the internal field separators used to delimit fields. RETURN VALUE
exits with one of the following values: 0 Successful completion. >0 End-of-file was detected or an error occurred. EXAMPLES
Print a file with the first field of each line moved to the end of the line. while read -r xx yy do printf "%s %s " "$yy" "$xx" done < input_file SEE ALSO
csh(1), ksh(1), sh(1), sh-posix(1). STANDARDS CONFORMANCE
read(1)
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