1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
|
#!/bin/bash
# badread.sh:
# Attempting to use 'echo and 'read'
#+ to assign variables non-interactively.
# shopt -s lastpipe
a=aaa
b=bbb
c=ccc
echo "one two three" | read a b c
# Try to reassign a, b, and c.
echo
echo "a = $a" # a = aaa
echo "b = $b" # b = bbb
echo "c = $c" # c = ccc
# Reassignment failed.
### However . . .
## Uncommenting line 6:
# shopt -s lastpipe
##+ fixes the problem!
### This is a new feature in Bash, version 4.2.
# ------------------------------
# Try the following alternative.
var=`echo "one two three"`
set -- $var
a=$1; b=$2; c=$3
echo "-------"
echo "a = $a" # a = one
echo "b = $b" # b = two
echo "c = $c" # c = three
# Reassignment succeeded.
# ------------------------------
# Note also that an echo to a 'read' works within a subshell.
# However, the value of the variable changes *only* within the subshell.
a=aaa # Starting all over again.
b=bbb
c=ccc
echo; echo
echo "one two three" | ( read a b c;
echo "Inside subshell: "; echo "a = $a"; echo "b = $b"; echo "c = $c" )
# a = one
# b = two
# c = three
echo "-----------------"
echo "Outside subshell: "
echo "a = $a" # a = aaa
echo "b = $b" # b = bbb
echo "c = $c" # c = ccc
echo
exit 0
|
