I was trying to execute some bash scripts in zsh (oh-my-zsh). I found ${TAIL} is not working in zsh.
bash:
bash-3.2$ ${CD} /tmp; echo "test" >> test.txt; ${TAIL} test.txt
bash: /tmp: is a directory
test
zsh:
~ ${CD} /tmp; echo "test" >> test.txt; ${TAIL} test.txt
zsh: command not found: tail -f
✘ /tmp
But using tail directly is fine
✘ /tmp tail -f test.txt
test
test
whereis tail
/usr/bin/tail
echo $PATH
/usr/local/bin:/usr/bin
I think this is a classic case in zsh for Why does $var where var="foo bar" not do what I expect?
Unlike bash, by default, zsh does not split into words when passed to a command or used in a loop as for foo in $var.
var="foo bar"
enabled the flag manually as
setopt shwordsplit
then try the same as
echo "test" >> test.txt; ${TAIL} test.txt
Related
The man page for echo says:
-n Do not print the trailing newline character. This may also be
achieved by appending `\c' to the end of the string, as is done by
iBCS2 compatible systems. Note that this option as well as the
effect of `\c' are implementation-defined in IEEE Std 1003.1-2001
(``POSIX.1'') as amended by Cor. 1-2002. Applications aiming for
maximum portability are strongly encouraged to use printf(1) to
suppress the newline character.
However this doesn't seem to work in sh on Mac:
sh-3.2$ echo $0
/bin/sh
sh-3.2$ which echo
/bin/echo
sh-3.2$ echo -n foo
-n foo
It works properly in bash:
bash-3.2$ echo $0
bash
bash-3.2$ which echo
/bin/echo
bash-3.2$ echo -n foo
foobash-3.2
FWIW this only seems to happen on Mac, on Linux it works properly:
$ echo $0
sh
$ echo -n foo
foo$
-n is a bash extension to echo. In version 3.2 (which ships with macOS), bash does not support the extension when invoked as sh. Starting with version 4.0 (some version of which is likely on your Linux box), bash does honor -n when invoked as sh.
Update: the xpg_echo option determines if bash's built-in echo is POSIX-compliant or not. In bash 3.2 (or at least the macOS build of 3.2), this option defaults to on; in bash 4.x, it defaults to off.
% sh -c 'shopt xpg_echo'
xpg_echo on
% ./sh -c 'shopt xpg_echo'
xpg_echo off
(./sh is a symlink to /usr/local/bin/bash, a local installation of bash 4.4 on my machine.)
I'm using ZSH.
Why does the last command not output anything?
$ cat create_foo.sh
foo=bar
$ source create_foo.sh && echo $foo
bar
$ unset foo
$ bash -c "source create_foo.sh && echo $foo"
From the last command I don't get any output.
Because $foo is getting substituted with an empty string in the double quotes.
You need to either use single quotes or escape the $ sign:
$ bash -c 'source create_foo.sh && echo $foo'
bar
$ bash -c "source create_foo.sh && echo \$foo"
bar
i have a bash script show below in a file called test.sh
#!/usr/bin/env bash
echo $1
echo "execution done"
when i execute this script using
Case-1
./test.sh "started"
started
execution done
showing properly
Case-2
If i execute with
bash test.sh "started"
i'm getting the out put as
started
execution done
But i would like to execute this using a cat or wget command with arguments
For example like.
Q1
cat test.sh |bash
Or using a command
Q2
wget -qO - "url contain bash" |bash
So in Q1 and Q2 how do i pass argument
Something simlar to this shown in this github
https://github.com/creationix/nvm
Please refer installation script
$ bash <(curl -Ls url_contains_bash_script) arg1 arg2
Explanation:
$ echo -e 'echo "$1"\necho "done"' >test.sh
$ cat test.sh
echo "$1"
echo "done"
$ bash <(cat test.sh) "hello"
hello
done
$ bash <(echo -e 'echo "$1"\necho "done"') "hello"
hello
done
You don't need to pipe to bash; bash runs as standard in your terminal.
If I have a script and I have to use cat, this is what I'll do:
cat script.sh > file.sh; chmod 755 file.sh; ./file.sh arg1 arg2 arg3
script.sh is the source script. You can replace that call with anything you want.
This has security implications though; just running an arbitrary code in your shell - especially with wget where the code comes from a remote location.
I am trying to run a command with a variable which holds another command that suppresses warning messages of the jar. However, it is not working as expected and I can't figure out what I am doing wrong.
TEST=${TEST:-2> /dev/null}
java -jar ~/bin/aw.jar ${Test}
Redirection is performed only if it is unquoted and present in the command line literally rather than originating from any kind of expansion:
$ ls
$ echo hello >out
$ ls
out
$ cat out
hello
$ rm *
$ echo hello '>out'
hello >out
$ ls
$ x='>out'
$ echo hello $x
hello >out
$ ls
In order to interpret redirection operator coming from a quoted string or an expansion you must execute the command through eval (note, however, that this may result in undesired expansions in other parts of your command):
$ ls
$ x='>out'
$ eval echo hello $x
$ ls
out
$ cat out
hello
In user's console I have bash:
$ echo $SHELL
/bin/bash
$ bash --version
GNU bash, version 4.2.46(1)-release (x86_64-redhat-linux-gnu)
I have code in file test.sh:
$ cat test.sh
aaa='---aa-aa---'
echo "${aaa}"
echo 'does not work...'
# trim "-"
echo ${aaa/+(-)}
echo ${aaa%%+(-)}
echo 'works for one symbol...'
echo ${aaa%-}
echo ${aaa/-}
The last two rows work fine but previous ones.
$ bash test.sh
---aa-aa---
does not work...
---aa-aa---
---aa-aa---
works for one symbol...
---aa-aa--
--aa-aa---
In the same time, if you would try to make this console it works:
$ aaa='---aa-aa---'
$ echo ${aaa/+(-)}
aa-aa---
$ echo ${aaa%%+(-)}
---aa-aa
So, why it doesn't work in a script?
You seem to have shopt -s extglob enabled in your interactive shell, which turns on extended globbing. This is not the default behavior, and needs to be explicitly enabled in your script. See extended pattern matching in the bash hackers wiki for details.