I'm writing a bash script that is supposed to be "transparent" to the user. It reads commands from the user and intercepts them, allowing only some of them to be executed by bash, depending on some criteria. It (basically) works like this:
while true; do
read COMMAND
can_be_done $COMMAND
if [ $? == 0 ]; then
eval $COMMAND
if [ $? != 0 ]; then
echo "Error: command not found"
fi
fi
done
The problem is, when the command fails, you also get stuff printed to the console. BUT, if I keep the result in a variable and only print it when it doesn't fail, like so:
RESULT=$(eval $COMMAND)
Then there's another problem: The special formatting gets lost (for example, "ls --color" doesn't show colors anymore)
My question is: Is there a way to have the command print to STDOUT if successful, but to /dev/null if it fails?
Do you really need the second part, replacing the output of the command with an error message? Linux commands print their own error messages, which aren't necessarily "command not found". You'd be hiding the true error (permission denied, file not found, out of memory, segfault, etc.) with an oftentimes incorrect error message (command not found).
If you remove that check, you could simplify the loop to something like this:
while true; do
read -e COMMAND
if can_be_done "$COMMAND"; then
eval "$COMMAND"
fi
done
read -e uses readline to obtain the command, making the prompt a lot more shell-like (↑ and ↓ for history, for instance).
command; if [ $? == 0 ]; then is more idiomatically written as if <command>; then.
Quoting makes sure special characters and whitespace are handled properly.
I would argue strongly that you should not do this. If you do not want to see output, redirect it to /dev/null. If you do want to see errors, do not redirect stderr. If you are using a program that prints its error messages on stdout instead of stderr, FIX THE PROGRAM! Error messages belong on stderr. Note that this means your program is broken, as it ought to read:
echo "Error: command not found" >&2
I'm not sure if it is rule number 1, but it certainly belongs in the top 10, and it may be the most often violated rule: Error messages belong on stderr. A program which prints error messages on stdout is broken.
if false > /dev/null;then echo 1; else echo 2; fi 2> /dev/null
Will output 2
if true > /dev/null;then echo 1; else echo 2; fi 2> /dev/null
Will output 1
remove the > /dev/null to print the command also to stdout
for example
if echo 123;then echo 1; else echo 2; fi 2> /dev/null
Will output
123 & 1
Assuming that the command is not very expensive to run you can do this:
test `ls /mooo 2>/dev/null` || echo moo not found
test will return true only if the command exits with 0, in this case ls is the command. You could have put this in an if statement too like so:
if [ `ls /moo 2>/dev/null` ];then
echo moo is a folder
fi
Related
I want to execute a long running command in Bash, and both capture its exit status, and tee its output.
So I do this:
command | tee out.txt
ST=$?
The problem is that the variable ST captures the exit status of tee and not of command. How can I solve this?
Note that command is long running and redirecting the output to a file to view it later is not a good solution for me.
There is an internal Bash variable called $PIPESTATUS; it’s an array that holds the exit status of each command in your last foreground pipeline of commands.
<command> | tee out.txt ; test ${PIPESTATUS[0]} -eq 0
Or another alternative which also works with other shells (like zsh) would be to enable pipefail:
set -o pipefail
...
The first option does not work with zsh due to a little bit different syntax.
Dumb solution: Connecting them through a named pipe (mkfifo). Then the command can be run second.
mkfifo pipe
tee out.txt < pipe &
command > pipe
echo $?
using bash's set -o pipefail is helpful
pipefail: the return value of a pipeline is the status of
the last command to exit with a non-zero status,
or zero if no command exited with a non-zero status
There's an array that gives you the exit status of each command in a pipe.
$ cat x| sed 's///'
cat: x: No such file or directory
$ echo $?
0
$ cat x| sed 's///'
cat: x: No such file or directory
$ echo ${PIPESTATUS[*]}
1 0
$ touch x
$ cat x| sed 's'
sed: 1: "s": substitute pattern can not be delimited by newline or backslash
$ echo ${PIPESTATUS[*]}
0 1
This solution works without using bash specific features or temporary files. Bonus: in the end the exit status is actually an exit status and not some string in a file.
Situation:
someprog | filter
you want the exit status from someprog and the output from filter.
Here is my solution:
((((someprog; echo $? >&3) | filter >&4) 3>&1) | (read xs; exit $xs)) 4>&1
echo $?
See my answer for the same question on unix.stackexchange.com for a detailed explanation and an alternative without subshells and some caveats.
By combining PIPESTATUS[0] and the result of executing the exit command in a subshell, you can directly access the return value of your initial command:
command | tee ; ( exit ${PIPESTATUS[0]} )
Here's an example:
# the "false" shell built-in command returns 1
false | tee ; ( exit ${PIPESTATUS[0]} )
echo "return value: $?"
will give you:
return value: 1
So I wanted to contribute an answer like lesmana's, but I think mine is perhaps a little simpler and slightly more advantageous pure-Bourne-shell solution:
# You want to pipe command1 through command2:
exec 4>&1
exitstatus=`{ { command1; printf $? 1>&3; } | command2 1>&4; } 3>&1`
# $exitstatus now has command1's exit status.
I think this is best explained from the inside out - command1 will execute and print its regular output on stdout (file descriptor 1), then once it's done, printf will execute and print icommand1's exit code on its stdout, but that stdout is redirected to file descriptor 3.
While command1 is running, its stdout is being piped to command2 (printf's output never makes it to command2 because we send it to file descriptor 3 instead of 1, which is what the pipe reads). Then we redirect command2's output to file descriptor 4, so that it also stays out of file descriptor 1 - because we want file descriptor 1 free for a little bit later, because we will bring the printf output on file descriptor 3 back down into file descriptor 1 - because that's what the command substitution (the backticks), will capture and that's what will get placed into the variable.
The final bit of magic is that first exec 4>&1 we did as a separate command - it opens file descriptor 4 as a copy of the external shell's stdout. Command substitution will capture whatever is written on standard out from the perspective of the commands inside it - but since command2's output is going to file descriptor 4 as far as the command substitution is concerned, the command substitution doesn't capture it - however once it gets "out" of the command substitution it is effectively still going to the script's overall file descriptor 1.
(The exec 4>&1 has to be a separate command because many common shells don't like it when you try to write to a file descriptor inside a command substitution, that is opened in the "external" command that is using the substitution. So this is the simplest portable way to do it.)
You can look at it in a less technical and more playful way, as if the outputs of the commands are leapfrogging each other: command1 pipes to command2, then the printf's output jumps over command 2 so that command2 doesn't catch it, and then command 2's output jumps over and out of the command substitution just as printf lands just in time to get captured by the substitution so that it ends up in the variable, and command2's output goes on its merry way being written to the standard output, just as in a normal pipe.
Also, as I understand it, $? will still contain the return code of the second command in the pipe, because variable assignments, command substitutions, and compound commands are all effectively transparent to the return code of the command inside them, so the return status of command2 should get propagated out - this, and not having to define an additional function, is why I think this might be a somewhat better solution than the one proposed by lesmana.
Per the caveats lesmana mentions, it's possible that command1 will at some point end up using file descriptors 3 or 4, so to be more robust, you would do:
exec 4>&1
exitstatus=`{ { command1 3>&-; printf $? 1>&3; } 4>&- | command2 1>&4; } 3>&1`
exec 4>&-
Note that I use compound commands in my example, but subshells (using ( ) instead of { } will also work, though may perhaps be less efficient.)
Commands inherit file descriptors from the process that launches them, so the entire second line will inherit file descriptor four, and the compound command followed by 3>&1 will inherit the file descriptor three. So the 4>&- makes sure that the inner compound command will not inherit file descriptor four, and the 3>&- will not inherit file descriptor three, so command1 gets a 'cleaner', more standard environment. You could also move the inner 4>&- next to the 3>&-, but I figure why not just limit its scope as much as possible.
I'm not sure how often things use file descriptor three and four directly - I think most of the time programs use syscalls that return not-used-at-the-moment file descriptors, but sometimes code writes to file descriptor 3 directly, I guess (I could imagine a program checking a file descriptor to see if it's open, and using it if it is, or behaving differently accordingly if it's not). So the latter is probably best to keep in mind and use for general-purpose cases.
(command | tee out.txt; exit ${PIPESTATUS[0]})
Unlike #cODAR's answer this returns the original exit code of the first command and not only 0 for success and 127 for failure. But as #Chaoran pointed out you can just call ${PIPESTATUS[0]}. It is important however that all is put into brackets.
In Ubuntu and Debian, you can apt-get install moreutils. This contains a utility called mispipe that returns the exit status of the first command in the pipe.
Outside of bash, you can do:
bash -o pipefail -c "command1 | tee output"
This is useful for example in ninja scripts where the shell is expected to be /bin/sh.
The simplest way to do this in plain bash is to use process substitution instead of a pipeline. There are several differences, but they probably don't matter very much for your use case:
When running a pipeline, bash waits until all processes complete.
Sending Ctrl-C to bash makes it kill all the processes of a pipeline, not just the main one.
The pipefail option and the PIPESTATUS variable are irrelevant to process substitution.
Possibly more
With process substitution, bash just starts the process and forgets about it, it's not even visible in jobs.
Mentioned differences aside, consumer < <(producer) and producer | consumer are essentially equivalent.
If you want to flip which one is the "main" process, you just flip the commands and the direction of the substitution to producer > >(consumer). In your case:
command > >(tee out.txt)
Example:
$ { echo "hello world"; false; } > >(tee out.txt)
hello world
$ echo $?
1
$ cat out.txt
hello world
$ echo "hello world" > >(tee out.txt)
hello world
$ echo $?
0
$ cat out.txt
hello world
As I said, there are differences from the pipe expression. The process may never stop running, unless it is sensitive to the pipe closing. In particular, it may keep writing things to your stdout, which may be confusing.
PIPESTATUS[#] must be copied to an array immediately after the pipe command returns.
Any reads of PIPESTATUS[#] will erase the contents.
Copy it to another array if you plan on checking the status of all pipe commands.
"$?" is the same value as the last element of "${PIPESTATUS[#]}",
and reading it seems to destroy "${PIPESTATUS[#]}", but I haven't absolutely verified this.
declare -a PSA
cmd1 | cmd2 | cmd3
PSA=( "${PIPESTATUS[#]}" )
This will not work if the pipe is in a sub-shell. For a solution to that problem,
see bash pipestatus in backticked command?
Base on #brian-s-wilson 's answer; this bash helper function:
pipestatus() {
local S=("${PIPESTATUS[#]}")
if test -n "$*"
then test "$*" = "${S[*]}"
else ! [[ "${S[#]}" =~ [^0\ ] ]]
fi
}
used thus:
1: get_bad_things must succeed, but it should produce no output; but we want to see output that it does produce
get_bad_things | grep '^'
pipeinfo 0 1 || return
2: all pipeline must succeed
thing | something -q | thingy
pipeinfo || return
Pure shell solution:
% rm -f error.flag; echo hello world \
| (cat || echo "First command failed: $?" >> error.flag) \
| (cat || echo "Second command failed: $?" >> error.flag) \
| (cat || echo "Third command failed: $?" >> error.flag) \
; test -s error.flag && (echo Some command failed: ; cat error.flag)
hello world
And now with the second cat replaced by false:
% rm -f error.flag; echo hello world \
| (cat || echo "First command failed: $?" >> error.flag) \
| (false || echo "Second command failed: $?" >> error.flag) \
| (cat || echo "Third command failed: $?" >> error.flag) \
; test -s error.flag && (echo Some command failed: ; cat error.flag)
Some command failed:
Second command failed: 1
First command failed: 141
Please note the first cat fails as well, because it's stdout gets closed on it. The order of the failed commands in the log is correct in this example, but don't rely on it.
This method allows for capturing stdout and stderr for the individual commands so you can then dump that as well into a log file if an error occurs, or just delete it if no error (like the output of dd).
It may sometimes be simpler and clearer to use an external command, rather than digging into the details of bash. pipeline, from the minimal process scripting language execline, exits with the return code of the second command*, just like a sh pipeline does, but unlike sh, it allows reversing the direction of the pipe, so that we can capture the return code of the producer process (the below is all on the sh command line, but with execline installed):
$ # using the full execline grammar with the execlineb parser:
$ execlineb -c 'pipeline { echo "hello world" } tee out.txt'
hello world
$ cat out.txt
hello world
$ # for these simple examples, one can forego the parser and just use "" as a separator
$ # traditional order
$ pipeline echo "hello world" "" tee out.txt
hello world
$ # "write" order (second command writes rather than reads)
$ pipeline -w tee out.txt "" echo "hello world"
hello world
$ # pipeline execs into the second command, so that's the RC we get
$ pipeline -w tee out.txt "" false; echo $?
1
$ pipeline -w tee out.txt "" true; echo $?
0
$ # output and exit status
$ pipeline -w tee out.txt "" sh -c "echo 'hello world'; exit 42"; echo "RC: $?"
hello world
RC: 42
$ cat out.txt
hello world
Using pipeline has the same differences to native bash pipelines as the bash process substitution used in answer #43972501.
* Actually pipeline doesn't exit at all unless there is an error. It executes into the second command, so it's the second command that does the returning.
Why not use stderr? Like so:
(
# Our long-running process that exits abnormally
( for i in {1..100} ; do echo ploop ; sleep 0.5 ; done ; exit 5 )
echo $? 1>&2 # We pass the exit status of our long-running process to stderr (fd 2).
) | tee ploop.out
So ploop.out receives the stdout. stderr receives the exit status of the long running process. This has the benefit of being completely POSIX-compatible.
(Well, with the exception of the range expression in the example long-running process, but that's not really relevant.)
Here's what this looks like:
...
ploop
ploop
ploop
ploop
ploop
ploop
ploop
ploop
ploop
ploop
5
Note that the return code 5 does not get output to the file ploop.out.
I have bash script with many lines of code and I need run it while it returns $? == 0, but in case if it has error I need stop it and exit with code 1?
The question is how to do it?
I tried to use set -e command, but Jenkins does not marks build as failed, for him it looks like Success
I also need to get the Error message to show it in my Jenkins log
I managed to get error code(in my case it will be 126), but how to get error message?
main file
fileWithError.sh
rc=$?; if [[ $rc != 0 ]]; then
echo "exit {$rc} ";
fi
fileWithError.sh
#!/bin/sh
set -e
echo "Test"
agjfsjgfshgd
echo "Test2"
echo "Test3"
Just add the command set -e to the beginning of the file
This should look something similar to this
#!/bin/sh
set -e
#...Your code...
I think you just want:
#!/bin/sh
while fileWithError.sh; do
sleep 1;
done
echo fileWithError.sh failed!! >&2
Note that if the script is written well, then the echo is
redundant as fileWithError.sh should have written a decent
error message already. Also, the sleep may not be needed, but is useful to prevent a fast loop if the script succeeds quickly.
You can get the explicit return value, but it requires a bit of refactoring.
#!/bin/sh
true
while test $? = 0; do fileWithError.sh; done
echo fileWithError.sh failed with status $?!! >&2
since the return value of the while script will be the
return value of sleep in the first construction.
Its not quite easy to get an error code only.
How about this ...
#!/bin/bash
Msg=$(fileWithError.sh 2>&1) # redirect all error messages to stdout
if [ "$?" -ne 0 ] # Not Equal
then
echo "$Msg"
exit 1
fi
exit 0
You catch all messages created by fileWithError.sh and if the programm returned an error code then you have the error message already saved in a variable.
But this will make a disadvantage, because you will temporary store all messages created by fileWithError.sh till the error appears.
You can filter the error message with echo "$Msg" |tail -n 1, but its not 100% save.
You should also do some changes in fileWithError.sh...
Switch set -e with trap "exit 1" ERR. this will close the script on errors.
Hope this will help.
In a book I'm reading the below line
ls "$1" 2>/dev/null | grep "$1" 2>/dev/null 1>&2
when written in a script - by the book it says "The command is executed to check whether the file passed as the command line argument exists. The standard error is redirected to /dev/null (the unix black hole), and standard output is redirected to standard error by using 1>&2. Thus, the command does not produce any output or error message; its only puprose is to set the command returns status value $?."
But running the code:
if [ $? -eq 0 ]
would I not know it otherwise, I have tried without the cmd at beginning and with it as well with having no impact on the results. I'm sure the author would have written for some purpose. I cannot just figure what?
This looks like a very bad book, giving code that noone sane would ever write to poorly illustrate concepts that are generally used in completely different ways in shell scripts.
The line:
ls "$1" 2>/dev/null | grep "$1" 2>/dev/null 1>&2
is as described -- it has no visible effect other than setting the return code. Is your question about what this does in detail to get a return code or something else?
The line:
if [ $? -eq 0 ]
is an incomplete fragment that checks the return code of the previous command. It's incomplete as there is no then or fi, without which the shell will reject it as a syntax error and not do anything (if you type the above at a prompt, you'll get the secondary prompt, telling you the shell is waiting for more input to get a complete command). So without more code there's no apparent effect. Something more complete like:
if [ $? -eq 0 ]; then echo YES; else echo NO; fi
would output YES or NO based on that return code.
A more sensible way of doing the 6 lines starting with the ls would be:
if [ ! -e "$1" ]; then
echo "$1: not found"
exit 1
fi
As to what the ls line actually does, it runs ls (list files) with the name in $1 as an argument, then uses grep to search that listing for the same filename.
So if the file does not exist, ls gives an error and outputs nothing, so the grep fails (setting $? to 1). If the filename exists and is not a directory, the grep will succeed (setting $? to 0). Finally, if the filename exists and is a directory, it will search the contents of that directory, looking for any file or subdirectory with the same name as a substring -- which is probably just a bug. In addition, if $1 is a string beginning with -, it will do something fairly useless and unpredictable.
Overall, a prime example of a shell script that should never be written -- any student that turned in such a monstrosity should get an immediate F.
How to disable stdout or stderr in bash scripts temporarily?
Of course the most common way is to redirect stdout or stderr to /dev/null.
But on some systems /dev/null may be unwritable for normal users.
I am writing some scripts that is aim to be portable, so I do not prefer using /dev/null
Some blogs/posts say that >&- can close stdout, but when I tried echo 123 >&- in a bash terminal, it just failed with the message "bash: echo: write error: Bad file descriptor"
Surely I can do it by redirecting stdout or stderr to a tmp file like this:
some_command > /tmp/null
But what I want is a more "elegant" way
I think perhaps I can achieve this by using pipe like this:
some_command | :
But in this way, it may "pollutes" the exit code of the original command
Here is a possible way to do what you want:
( my_cmd 3>&1 1>&2 2>&3- ) | :
This temporarily send stdout to a new file handle, 3 and redirect stderr to stdout so that the stderr pipes into the command (in this case, :). Then the new file handle is routed back out to stdout. These avoid piping the stdout of my_cmd into :. The - in closes the handle after it's used.
To check the exist status of my_cmd after the above you examine the environment variable $PIPESTATUS[0]. $PIPESTATUS is a bash environment array variable that holds the exit status of each piped command in the last pipe that was done.
I think the really correct answer is to investigate why /dev/null isn't world writable. Having it not so is an off-standard system configuration and may cause system problems. The above work-around is a little messy by comparison.
Based on what I wrote earlier and #nos's comment above, here's an example:
(assuming you have no file called 'zzz' in your current directory, and that '.' is readable)
#!/bin/bash
set -o pipefail
ls . 2>&1 |:
echo $?
ls zzz 2>&1 |:
echo $?
The pipelines succeed and fail silently and maintain the exit code. Note that you can probably still make a pipeline example where this would not produce the desired results. I haven't come up with one in my head yet, but that doesn't mean it's not out there. The best answer, as many have noted already, is to fix the system so that /dev/null is world writable.
EDIT: Changed /bin/sh to /bin/bash, although this probably isn't necessary. But since I haven't tested this against a true Bourne Shell, I decided to err on the side of caution.
EDIT: Another script, showing several different redirections, and using the |& shortcut for 2>&1 |. If you run this, you'll notice that some of the ls failures return a 141 exit status rather than the expected 2. This is a broken pipe exit status, but still represents a failure.
#!/bin/bash
set -o pipefail
# start with commands that should succeed
# redirect everything to ':'
echo "ls . |& :"
ls . |& :
echo $?
# redirect only stdout to ':'
echo "ls . | :"
ls . | :
echo $?
# redirect only stderr to ':'
echo "((ls . 1>&3) |& : ) 3>&1"
((ls . 1>&3) |& : ) 3>&1
echo $?
# now move to failures
# redirect everything to ':'
echo "ls zzz |& :"
ls zzz |& :
echo $?
# redirect only stdout to ':'
echo "ls zzz |:"
ls zzz |:
echo $?
# redirect only stderr to ':'
echo "((ls zzz 1>&3) |& : ) 3>&1"
((ls zzz 1>&3) |& : ) 3>&1
echo $?
I use two subshells when I'm attempting to destroy stdout but keep stderr. You could do it without the outer one. In fact, that might be better. Instead of getting a broken pipe error, you get a 1 exit status.
I have a Bash shell script that invokes a number of commands.
I would like to have the shell script automatically exit with a return value of 1 if any of the commands return a non-zero value.
Is this possible without explicitly checking the result of each command?
For example,
dosomething1
if [[ $? -ne 0 ]]; then
exit 1
fi
dosomething2
if [[ $? -ne 0 ]]; then
exit 1
fi
Add this to the beginning of the script:
set -e
This will cause the shell to exit immediately if a simple command exits with a nonzero exit value. A simple command is any command not part of an if, while, or until test, or part of an && or || list.
See the bash manual on the "set" internal command for more details.
It's really annoying to have a script stubbornly continue when something fails in the middle and breaks assumptions for the rest of the script. I personally start almost all portable shell scripts with set -e.
If I'm working with bash specifically, I'll start with
set -Eeuo pipefail
This covers more error handling in a similar fashion. I consider these as sane defaults for new bash programs. Refer to the bash manual for more information on what these options do.
To add to the accepted answer:
Bear in mind that set -e sometimes is not enough, specially if you have pipes.
For example, suppose you have this script
#!/bin/bash
set -e
./configure > configure.log
make
... which works as expected: an error in configure aborts the execution.
Tomorrow you make a seemingly trivial change:
#!/bin/bash
set -e
./configure | tee configure.log
make
... and now it does not work. This is explained here, and a workaround (Bash only) is provided:
#!/bin/bash
set -e
set -o pipefail
./configure | tee configure.log
make
The if statements in your example are unnecessary. Just do it like this:
dosomething1 || exit 1
If you take Ville Laurikari's advice and use set -e then for some commands you may need to use this:
dosomething || true
The || true will make the command pipeline have a true return value even if the command fails so the the -e option will not kill the script.
If you have cleanup you need to do on exit, you can also use 'trap' with the pseudo-signal ERR. This works the same way as trapping INT or any other signal; bash throws ERR if any command exits with a nonzero value:
# Create the trap with
# trap COMMAND SIGNAME [SIGNAME2 SIGNAME3...]
trap "rm -f /tmp/$MYTMPFILE; exit 1" ERR INT TERM
command1
command2
command3
# Partially turn off the trap.
trap - ERR
# Now a control-C will still cause cleanup, but
# a nonzero exit code won't:
ps aux | grep blahblahblah
Or, especially if you're using "set -e", you could trap EXIT; your trap will then be executed when the script exits for any reason, including a normal end, interrupts, an exit caused by the -e option, etc.
The $? variable is rarely needed. The pseudo-idiom command; if [ $? -eq 0 ]; then X; fi should always be written as if command; then X; fi.
The cases where $? is required is when it needs to be checked against multiple values:
command
case $? in
(0) X;;
(1) Y;;
(2) Z;;
esac
or when $? needs to be reused or otherwise manipulated:
if command; then
echo "command successful" >&2
else
ret=$?
echo "command failed with exit code $ret" >&2
exit $ret
fi
Run it with -e or set -e at the top.
Also look at set -u.
On error, the below script will print a RED error message and exit.
Put this at the top of your bash script:
# BASH error handling:
# exit on command failure
set -e
# keep track of the last executed command
trap 'LAST_COMMAND=$CURRENT_COMMAND; CURRENT_COMMAND=$BASH_COMMAND' DEBUG
# on error: print the failed command
trap 'ERROR_CODE=$?; FAILED_COMMAND=$LAST_COMMAND; tput setaf 1; echo "ERROR: command \"$FAILED_COMMAND\" failed with exit code $ERROR_CODE"; put sgr0;' ERR INT TERM
An expression like
dosomething1 && dosomething2 && dosomething3
will stop processing when one of the commands returns with a non-zero value. For example, the following command will never print "done":
cat nosuchfile && echo "done"
echo $?
1
#!/bin/bash -e
should suffice.
I am just throwing in another one for reference since there was an additional question to Mark Edgars input and here is an additional example and touches on the topic overall:
[[ `cmd` ]] && echo success_else_silence
Which is the same as cmd || exit errcode as someone showed.
For example, I want to make sure a partition is unmounted if mounted:
[[ `mount | grep /dev/sda1` ]] && umount /dev/sda1