Is there an alternative for the timeout command on Mac OSx. The basic requirement is I am able to run a command for a specified amount of time.
e.g:
timeout 10 ping google.com
This program runs ping for 10s on Linux.
You can use
brew install coreutils
And then whenever you need timeout, use
gtimeout
..instead. To explain why here's a snippet from the Homebrew Caveats section:
Caveats
All commands have been installed with the prefix 'g'.
If you really need to use these commands with their normal names, you
can add a "gnubin" directory to your PATH from your bashrc like:
PATH="/usr/local/opt/coreutils/libexec/gnubin:$PATH"
Additionally, you can access their man pages with normal names if you add
the "gnuman" directory to your MANPATH from your bashrc as well:
MANPATH="/usr/local/opt/coreutils/libexec/gnuman:$MANPATH"
Another simple approach that works pretty much cross platform (because it uses perl which is nearly everywhere) is this:
function timeout() { perl -e 'alarm shift; exec #ARGV' "$#"; }
Snagged from here:
https://gist.github.com/jaytaylor/6527607
Instead of putting it in a function, you can just put the following line in a script, and it'll work too:
timeout.sh
perl -e 'alarm shift; exec #ARGV' "$#";
or a version that has built in help/examples:
timeout.sh
#!/usr/bin/env bash
function show_help()
{
IT=$(cat <<EOF
Runs a command, and times out if it doesnt complete in time
Example usage:
# Will fail after 1 second, and shows non zero exit code result
$ timeout 1 "sleep 2" 2> /dev/null ; echo \$?
142
# Will succeed, and return exit code of 0.
$ timeout 1 sleep 0.5; echo \$?
0
$ timeout 1 bash -c 'echo "hi" && sleep 2 && echo "bye"' 2> /dev/null; echo \$?
hi
142
$ timeout 3 bash -c 'echo "hi" && sleep 2 && echo "bye"' 2> /dev/null; echo \$?
hi
bye
0
EOF
)
echo "$IT"
exit
}
if [ "$1" == "help" ]
then
show_help
fi
if [ -z "$1" ]
then
show_help
fi
#
# Mac OS-X does not come with the delightfully useful `timeout` program. Thankfully a rough BASH equivalent can be achieved with only 2 perl statements.
#
# Originally found on SO: http://stackoverflow.com/questions/601543/command-line-command-to-auto-kill-a-command-after-a-certain-amount-of-time
#
perl -e 'alarm shift; exec #ARGV' "$#";
As kvz stated simply use homebrew:
brew install coreutils
Now the timeout command is already ready to use - no aliases are required (and no gtimeout required, although also available).
You can limit execution time of any program using this command:
ping -t 10 google.com & sleep 5; kill $!
The Timeout Package from Ubuntu / Debian can be made to compile on Mac and it works.
The package is available at http://packages.ubuntu.com/lucid/timeout
You can do ping -t 10 google.com >nul
the >nul gets rid of the output. So instead of showing 64 BYTES FROM 123.45.67.8 BLAH BLAH BLAH it'll just show a blank newline until it times out. -t flag can be changed to any number.
Related
Here I am again. Today I wrote a little script that is supposed to start an application silently in my debian env.
Easy as
silent "npm search 1234556"
This works but not at all.
As you can see, I commented the section where I have some troubles.
This line:
$($cmdLine) &
doesn't hide application output but this one
$($1 >/dev/null 2>/dev/null) &
works perfectly. What am I missing? Many thanks.
#!/bin/sh
# Daniele Brugnara
# October, 2013
# Silently exec a command line passed as argument
errorsRedirect=""
if [ -z "$1" ]; then
echo "Please, don't joke me..."
exit 1
fi
cmdLine="$1 >/dev/null"
# if passed a second parameter, errors will be hidden
if [ -n "$2" ]; then
cmdLine="$cmdLine 2>/dev/null"
fi
# not working
$($cmdLine) &
# works perfectly
#$($1 >/dev/null 2>/dev/null) &
With the use of evil eval following script will work:
#!/bin/sh
# Silently exec a command line passed as argument
errorsRedirect=""
if [ -z "$1" ]; then
echo "Please, don't joke me..."
exit 1
fi
cmdLine="$1 >/dev/null"
# if passed a second parameter, errors will be hidden
if [ -n "$2" ]; then
cmdLine="$cmdLine 2>&1"
fi
eval "$cmdLine &"
Rather than building up a command with redirection tacked on the end, you can incrementally apply it:
#!/bin/sh
if [ -z "$1" ]; then
exit
fi
exec >/dev/null
if [ -n "$2" ]; then
exec 2>&1
fi
exec $1
This first redirects stdout of the shell script to /dev/null. If the second argument is given, it redirects stderr of the shell script too. Then it runs the command which will inherit stdout and stderr from the script.
I removed the ampersand (&) since being silent has nothing to do with running in the background. You can add it back (and remove the exec on the last line) if it is what you want.
I added exec at the end as it is slightly more efficient. Since it is the end of the shell script, there is nothing left to do, so you may as well be done with it, hence exec.
& means that you're doing sort of multitask whereas
1 >/dev/null 2>/dev/null
means that you redirect the output to a sort of garbage and that's why you don't see anything.
Furthermore cmdLine="$1 >/dev/null" is incorrect, you should use ' instead of " :
cmdLine='$1 >/dev/null'
you can build your command line in a var and run a bash with it in background:
bash -c "$cmdLine"&
Note that it might be useful to store the output (out/err) of the program, instead of trow them in null.
In addition, why do you need errorsRedirect??
You can even add a wait at the end, just to be safe...if you want...
#!/bin/sh
# Daniele Brugnara
# October, 2013
# Silently exec a command line passed as argument
[ ! $1 ] && echo "Please, don't joke me..." && exit 1
cmdLine="$1>/dev/null"
# if passed a second parameter, errors will be hidden
[ $2 ] && cmdLine+=" 2>/dev/null"
# not working
echo "Running \"$cmdLine\""
bash -c "$cmdLine" &
wait
I'm writing a shell script that loops over some values and run a long command line for each value. I'd like to print out these commands along the way, just like make does when running a makefile. I know I could just "echo" all commands before running them, but it feels inelegant. So I'm looking at set -x and similar mechanisms instead :
#!/bin/sh
for value in a long list of values
do
set -v
touch $value # imagine a complicated invocation here
set +v
done
My problem is: at each iteration, not only is the interresting line printed out, but also the set +x line as well. Is it somehow possible to prevent that ? If not, what workaround do you recommend ?
PS: the MWE above uses sh, but I also have bash and zsh installed in case that helps.
Sandbox it in a subshell:
(set -x; do_thing_you_want_traced)
Of course, changes to variables or the environment made in that subshell will be lost.
If you REALLY care about this, you could also use a DEBUG trap (using set -T to cause it to be inherited by functions) to implement your own set -x equivalent.
For instance, if using bash:
trap_fn() {
[[ $DEBUG && $BASH_COMMAND != "unset DEBUG" ]] && \
printf "[%s:%s] %s\n" "$BASH_SOURCE" "$LINENO" "$BASH_COMMAND"
return 0 # do not block execution in extdebug mode
}
trap trap_fn DEBUG
DEBUG=1
# ...do something you want traced...
unset DEBUG
That said, emitting BASH_COMMAND (as a DEBUG trap can do) is not fully equivalent of set -x; for instance, it does not show post-expansion values.
You want to try using a single-line xtrace:
function xtrace() {
# Print the line as if xtrace was turned on, using perl to filter out
# the extra colon character and the following "set +x" line.
(
set -x
# Colon is a no-op in bash, so nothing will execute.
: "$#"
set +x
) 2>&1 | perl -ne 's/^[+] :/+/ and print' 1>&2
# Execute the original line unmolested
"$#"
}
The original command executes in the same shell under an identity transformation. Just prior to running, you get a non-recursive xtrace of the arguments. This allows you to xtrace the commands you care about without spamming stederr with duplicate copies of every "echo" command.
# Example
for value in $long_list; do
computed_value=$(echo "$value" | sed 's/.../...')
xtrace some_command -x -y -z $value $computed_value ...
done
Next command disables 'xtrace' option:
$ set +o xtrace
I thought of
set -x >/dev/null 2>1; echo 1; echo 2; set +x >/dev/null 2>&1
but got
+ echo 1
1
+ echo 2
2
+ 1> /dev/null 2>& 1
I'm surprised by these results. .... But
set -x ; echo 1; echo 2; set +x
+ echo 1
1
+ echo 2
2
looks to meet your requirement.
I saw similar results when I put each statement on its only line (excepting the set +x)
IHTH.
I want my shell to detect if human behavior, then show the prompt.
So, assume the file name is test.bash
#!/bin/bash
if [ "x" != "${PS1:-x}" ] ;then
read -p "remove test.log Yes/No" x
[ "$x" = "n" ] && exit 1
fi
rm -f test.log
But, I found it can not work if I haven't set PS1. Is there better method?
my test methods:
./test.bash # human interactive
./test.bash > /tmp/test.log # stdout in batch mode
ls | ./test.bash # stdin in batch mode
to elaborate, I would try
if [ -t 0 ] ; then
# this shell has a std-input, so we're not in batch mode
.....
else
# we're in batch mode
....
fi
I hope this helps.
From help test:
-t FD True if FD is opened on a terminal.
You could make use of the /usr/bin/tty program:
if tty -s
then
# ...
fi
I admit that I'm not sure how portable it is, but it's at least part of GNU coreutils.
Note that in bash scripts (see the test expr entry in man bash), it is not necessary to use the beefy && and || shell operators to combine two separate runs of the [ command, because the [ command has its own built-in and -a and or -o operators that let you compose several simpler tests into a single outcome.
So, here is how you can implement the test that you asked for — where you flip into batch mode if either the input or the output has been redirected away from the TTY — using a single invocation of [:
if [ -t 0 -a -t 1 ]
then
echo Interactive mode
else
echo Batch mode
fi
My connection is flaky, however I have a backup one. I made some bash script to check for connectivity and change connection if the present one is dead. Please help me improve them.
The scripts almost works, except for not waiting long enough to receive an IP (it cycles to next step in the until loop too quick). Here goes:
#!/bin/bash
# Invoke this script with paths to your connection specific scripts, for example
# ./gotnet.sh ./connection.sh ./connection2.sh
until [ -z "$1" ] # Try different connections until we are online...
do
if eval "ping -c 1 google.com"
then
echo "we are online!" && break
else
$1 # Runs (next) connection-script.
echo
fi
shift
done
echo # Extra line feed.
exit 0
And here is an example of the slave scripts:
#!/bin/bash
ifconfig wlan0 down
ifconfig wlan0 up
iwconfig wlan0 key 1234567890
iwconfig wlan0 essid example
sleep 1
dhclient -1 -nw wlan0
sleep 3
exit 0
Here's one way to do it:
#!/bin/bash
while true; do
if ! [ "`ping -c 1 google.com; echo $?`" ]; then #if ping exits nonzero...
./connection_script1.sh #run the first script
sleep 10 #give it a few seconds to complete
fi
if ! [ "`ping -c 1 google.com; echo $?`" ]; then #if ping *still* exits nonzero...
./connection_script2.sh #run the second script
sleep 10 #give it a few seconds to complete
fi
sleep 300 #check again in five minutes
done
Adjust the sleep times and ping count to your preference. This script never exits so you would most likely want to run it with the following command:
./connection_daemon.sh 2>&1 > /dev/null & disown
Have you tried omitting the -nw option from the dhclient command?
Also, remove the eval and quotes from your if they aren't necessary. Do it like this:
if ping -c 1 google.com > /dev/null 2>&1
Trying using ConnectTimeout ${timeout} somewhere.
Suppose a shell script (/bin/sh or /bin/bash) contained several commands. How can I cleanly make the script terminate if any of the commands has a failing exit status? Obviously, one can use if blocks and/or callbacks, but is there a cleaner, more concise way? Using && is not really an option either, because the commands can be long, or the script could have non-trivial things like loops and conditionals.
With standard sh and bash, you can
set -e
It will
$ help set
...
-e Exit immediately if a command exits with a non-zero status.
It also works (from what I could gather) with zsh. It also should work for any Bourne shell descendant.
With csh/tcsh, you have to launch your script with #!/bin/csh -e
May be you could use:
$ <any_command> || exit 1
You can check $? to see what the most recent exit code is..
e.g
#!/bin/sh
# A Tidier approach
check_errs()
{
# Function. Parameter 1 is the return code
# Para. 2 is text to display on failure.
if [ "${1}" -ne "0" ]; then
echo "ERROR # ${1} : ${2}"
# as a bonus, make our script exit with the right error code.
exit ${1}
fi
}
### main script starts here ###
grep "^${1}:" /etc/passwd > /dev/null 2>&1
check_errs $? "User ${1} not found in /etc/passwd"
USERNAME=`grep "^${1}:" /etc/passwd|cut -d":" -f1`
check_errs $? "Cut returned an error"
echo "USERNAME: $USERNAME"
check_errs $? "echo returned an error - very strange!"