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Full Discussion: Can I use read to read content of a variable
Top Forums Shell Programming and Scripting Can I use read to read content of a variable Post 302301076 by mjd_tech on Wednesday 25th of March 2009 07:49:24 PM
Old 03-25-2009
Oops, I forgot to quote ALL the vars...

Ksh version:
Code:
#!/bin/ksh
IFS="~"
VAR1="1~2~3~4"

echo "$VAR1" | read a b c d
echo "$a $b $c $d"
echo "$a"

# Result
1 2 3 4
1

Bash / Dash version (no pipe, no brackets)
Code:
#!/bin/sh
IFS="~"
VAR1="1~2~3~4"

read a b c d <<EOF
$(echo "$VAR1")
EOF
echo "$a $b $c $d"
echo "$a"

# Result
1 2 3 4
1

  • The Bash version works in ksh
  • The ksh version does not work in Bash.
This is because Bash creates a subshell for the last process in a pipeline, in this case the read statement.

Thus, the variables a b c d would only be visible to the subshell. I used brackets in the earlier Bash example to group read and echo commands in the same subshell.

In this example, I used a "here document" to feed the read command, instead of a pipe. Thus, the read command does not happen in a subshell, and the a b c d variables are visible to the rest of the script.

Hopefully this makes sense.
 

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LEARN ABOUT OSF1

line

line(1) 						      General Commands Manual							   line(1)

NAME

       line - Reads one line from standard input

SYNOPSIS

       line

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       line:  XCU5.0

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

OPTIONS

       None

DESCRIPTION

       The  line  command  copies one line, up to and including a newline, from standard input and writes it to standard output.  Use this command
       within a shell command file to read from your terminal.	The line command always writes at least a newline character.

NOTES

       The line utility has no internationalization features and is marked LEGACY in XCU Issue 5. Use the read utility instead.

EXIT STATUS

       Success.  End-of-File.

EXAMPLES

       To read a line from the keyboard and append it to a file, enter: echo 'Enter comments for the log:' echo ': c' line >>log

       This shell procedure displays the message: Enter comments for the log:

       It then reads a line of text from the keyboard and adds it to the end of the file log.  The echo  ':  c'  command  displays  a	:  (colon)
       prompt.	See the echo command for information about the c escape sequence.

SEE ALSO

       Commands:  echo(1), ksh(1), read(1), Bourne shell sh(1b), POSIX shell sh(1p)

       Functions:  read(2)

       Standards:  standards(5)

																	   line(1)
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