Menachem Shapiro wrote:
>
> I came across this site that lists some common Bash pitfalls, as well
> as the correct way of doing things:
> http://wooledge.org/mywiki/BashPitfalls
Top 4 reasons why zsh is better than bash:
2) cp $file $target
Under bash, this will split the words on whitespace. In zsh, there
will be no word splitting by default.
file="file one.txt"; target="file two.txt"
$ cp $file $target
cp: target `two.txt' is not a directory
% cp $file $target
% ls -b $file $target
file\ one.txt file\ two.txt
3) [ $foo = "bar" ]
Under bash, $foo will be susceptible to word splitting. Under zsh, it
is not. The quotes are superfluous, in either shell.
foo="two words"
$ [ $foo = "bar" ]
bash: [: too many arguments
% [ $foo = "bar" ]
% echo $?
1
Because $foo did not contain the value bar, the comparison failed.
7) grep foo bar | while read line; do ((count++)); done
Under bash, the value of count will not have changed as the pipelines
are under subshells. zsh does not do this.
for i in 1 2 3; do echo foo; done > bar
unset count
$ grep foo bar | while read line; do ((count++)); done
$ echo :$count:
::
% grep foo bar | while read line; do ((count++)); done
% echo :$count:
:3:
19) for i in {1..10}; do ./something &; done
Inside of bash, it is illegal to place a ; directly after a &, as
they both terminate the command.
zsh allows this.
cat <<EOF >something; chmod +x something
> #!/bin/sh
> echo -n .; sleep 10
> EOF
$ for i in {1..10}; do ./something &; done
bash: syntax error near unexpected token `;'
% for i in {1..10}; do ./something &; done
.[2] 24209
.[3] 24211
.[4] 24213
[5] 24215
.[6] 24216
.[7] 24218
.[8] 24220
.[9] 24222
[10] 24224
..[11] 24225
.
Some people may decry that zsh does not split on whitespace, inside a
variable, so they can't do a="1 2 3 4 5"; for i in $a; do [something
five time]; done. This is a throwback to sh, when there were no arrays,
so the scalars were overloaded to be arrays, and bash continues this
dubious tradition.
% a=(1 2 3 4 5); for i in $a; do [something five times]; done
All I did was change the "" to (). This has the added benefit of
allowing white space in the array values itself:
% a=("1 one" "2 two" "3 three" "4 four" "5 five");
% echo $a[5]
5 five
Bash also has arrays:
$ a=("1 one" "2 two" "3 three" "4 four" "5 five");
$ echo ${a[4]}
5 five
$ echo $a
1 one
$ echo ${a[*]}
1 one 2 two 3 three 4 four 5 five
The two are equivalent between zsh and bash array expansion:
zsh: $a
bash: "[EMAIL PROTECTED]"
$ for i in "[EMAIL PROTECTED]"; do echo :"$i":;done
For fun, try removing the quotes. Try replacing the @ with *. Make a
table!
for echo expected result actual result
1) "[EMAIL PROTECTED]" :"$i":
2) "[EMAIL PROTECTED]" :$i:
3) [EMAIL PROTECTED] :"$i":
4) [EMAIL PROTECTED] :$i:
5) "${a[*]}" :"$i":
6) "${a[*]}" :$i:
7) ${a[*]} :"$i":
8) ${a[*]} :$i:
-john
chsh -s "`command which zsh`"
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