If errexit is on, how do I run a command that might fail and get its exit code? - bash

All of my scripts have errexit turned on; that is, I run set -o errexit. However, sometimes I want to run commands like grep, but want to continue execution of my script even if the command fails.
How do I do this? That is, how can I get the exit code of a command into a variable without killing my whole script?
I could turn errexit off, but I'd prefer not to.

Your errexit will only cause the script to terminate if the command that fails is "untested". Per man sh on FreeBSD:
Exit immediately if any untested command fails in non-interactive
mode. The exit status of a command is considered to be explic-
itly tested if the command is part of the list used to control an
if, elif, while, or until; if the command is the left hand oper-
and of an ``&&'' or ``||'' operator; or if the command is a pipe-
line preceded by the ! keyword.
So .. if you were thinking of using a construct like this:
grep -q something /path/to/somefile
retval=$?
if [ $retval -eq 0 ]; then
do_something # found
else
do_something_else # not found
fi
you should instead use a construct like this:
if grep -q something /path/to/somefile; then
do_something # found
else
do_something_else # not found
fi
The existence of the if keyword makes the grep command tested, thus unaffected by errexit. And this way takes less typing.
Of course, if you REALLY need the exit value in a variable, there's nothing stopping you from using $?:
if grep -q something /path/to/somefile; then
do_something # found
else
unnecessary=$?
do_something $unnecessary # not found
fi

Here's a way to achieve this: you can "turn off" set -o errexit for some lines of code, and then turn it on again when you decide:
set +e #disables set -o errexit
grep -i something file.txt
rc="$?" #capturing the return code for last command
set -e #reenables set -o errexit
Another option would be the following:
grep -i something file.txt || rc="$?"
That would allow you to capture the return code on the variable rc, without interrupting your script. You could even extend this last option to capture and process the return code on the same line without risking to trigger an exit:
grep -i something file.txt || rc="$?" && echo rc="$?" > somefile.txt && command || :
The last bit ||: will guarantee that the line above always returns a return code = 0 (true).

The most compact and least repetitive form I can think of:
<command> && rc=$? || rc=$?
A form without variable name repetition -- rc=$(<command> && echo $? || echo $?) -- has an expression rvalue but would also capture the stdout of <command>1. So, it's only safe if you "know" that <command> has no normal output.
Using the a && b || c construct is safe here because rc=$? and $(echo $?) can never fail.
1Sure, you can work around this by fiddling with file descriptors, but that'd make the construct long-winded and inconvenient as a standard

Related

How to exit gitlab job when script fails [duplicate]

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

`grep` cause bash script stop [duplicate]

I'm studying the content of this preinst file that the script executes before that package is unpacked from its Debian archive (.deb) file.
The script has the following code:
#!/bin/bash
set -e
# Automatically added by dh_installinit
if [ "$1" = install ]; then
if [ -d /usr/share/MyApplicationName ]; then
echo "MyApplicationName is just installed"
return 1
fi
rm -Rf $HOME/.config/nautilus-actions/nautilus-actions.conf
rm -Rf $HOME/.local/share/file-manager/actions/*
fi
# End automatically added section
My first query is about the line:
set -e
I think that the rest of the script is pretty simple: It checks whether the Debian/Ubuntu package manager is executing an install operation. If it is, it checks whether my application has just been installed on the system. If it has, the script prints the message "MyApplicationName is just installed" and ends (return 1 mean that ends with an “error”, doesn’t it?).
If the user is asking the Debian/Ubuntu package system to install my package, the script also deletes two directories.
Is this right or am I missing something?
From help set :
-e Exit immediately if a command exits with a non-zero status.
But it's considered bad practice by some (bash FAQ and irc freenode #bash FAQ authors). It's recommended to use:
trap 'do_something' ERR
to run do_something function when errors occur.
See http://mywiki.wooledge.org/BashFAQ/105
set -e stops the execution of a script if a command or pipeline has an error - which is the opposite of the default shell behaviour, which is to ignore errors in scripts. Type help set in a terminal to see the documentation for this built-in command.
I found this post while trying to figure out what the exit status was for a script that was aborted due to a set -e. The answer didn't appear obvious to me; hence this answer. Basically, set -e aborts the execution of a command (e.g. a shell script) and returns the exit status code of the command that failed (i.e. the inner script, not the outer script).
For example, suppose I have the shell script outer-test.sh:
#!/bin/sh
set -e
./inner-test.sh
exit 62;
The code for inner-test.sh is:
#!/bin/sh
exit 26;
When I run outer-script.sh from the command line, my outer script terminates with the exit code of the inner script:
$ ./outer-test.sh
$ echo $?
26
As per bash - The Set Builtin manual, if -e/errexit is set, the shell exits immediately if a pipeline consisting of a single simple command, a list or a compound command returns a non-zero status.
By default, the exit status of a pipeline is the exit status of the last command in the pipeline, unless the pipefail option is enabled (it's disabled by default).
If so, the pipeline's return status of the last (rightmost) command to exit with a non-zero status, or zero if all commands exit successfully.
If you'd like to execute something on exit, try defining trap, for example:
trap onexit EXIT
where onexit is your function to do something on exit, like below which is printing the simple stack trace:
onexit(){ while caller $((n++)); do :; done; }
There is similar option -E/errtrace which would trap on ERR instead, e.g.:
trap onerr ERR
Examples
Zero status example:
$ true; echo $?
0
Non-zero status example:
$ false; echo $?
1
Negating status examples:
$ ! false; echo $?
0
$ false || true; echo $?
0
Test with pipefail being disabled:
$ bash -c 'set +o pipefail -e; true | true | true; echo success'; echo $?
success
0
$ bash -c 'set +o pipefail -e; false | false | true; echo success'; echo $?
success
0
$ bash -c 'set +o pipefail -e; true | true | false; echo success'; echo $?
1
Test with pipefail being enabled:
$ bash -c 'set -o pipefail -e; true | false | true; echo success'; echo $?
1
This is an old question, but none of the answers here discuss the use of set -e aka set -o errexit in Debian package handling scripts. The use of this option is mandatory in these scripts, per Debian policy; the intent is apparently to avoid any possibility of an unhandled error condition.
What this means in practice is that you have to understand under what conditions the commands you run could return an error, and handle each of those errors explicitly.
Common gotchas are e.g. diff (returns an error when there is a difference) and grep (returns an error when there is no match). You can avoid the errors with explicit handling:
diff this that ||
echo "$0: there was a difference" >&2
grep cat food ||
echo "$0: no cat in the food" >&2
(Notice also how we take care to include the current script's name in the message, and writing diagnostic messages to standard error instead of standard output.)
If no explicit handling is really necessary or useful, explicitly do nothing:
diff this that || true
grep cat food || :
(The use of the shell's : no-op command is slightly obscure, but fairly commonly seen.)
Just to reiterate,
something || other
is shorthand for
if something; then
: nothing
else
other
fi
i.e. we explicitly say other should be run if and only if something fails. The longhand if (and other shell flow control statements like while, until) is also a valid way to handle an error (indeed, if it weren't, shell scripts with set -e could never contain flow control statements!)
And also, just to be explicit, in the absence of a handler like this, set -e would cause the entire script to immediately fail with an error if diff found a difference, or if grep didn't find a match.
On the other hand, some commands don't produce an error exit status when you'd want them to. Commonly problematic commands are find (exit status does not reflect whether files were actually found) and sed (exit status won't reveal whether the script received any input or actually performed any commands successfully). A simple guard in some scenarios is to pipe to a command which does scream if there is no output:
find things | grep .
sed -e 's/o/me/' stuff | grep ^
It should be noted that the exit status of a pipeline is the exit status of the last command in that pipeline. So the above commands actually completely mask the status of find and sed, and only tell you whether grep finally succeeded.
(Bash, of course, has set -o pipefail; but Debian package scripts cannot use Bash features. The policy firmly dictates the use of POSIX sh for these scripts, though this was not always the case.)
In many situations, this is something to separately watch out for when coding defensively. Sometimes you have to e.g. go through a temporary file so you can see whether the command which produced that output finished successfully, even when idiom and convenience would otherwise direct you to use a shell pipeline.
I believe the intention is for the script in question to fail fast.
To test this yourself, simply type set -e at a bash prompt. Now, try running ls. You'll get a directory listing. Now, type lsd. That command is not recognized and will return an error code, and so your bash prompt will close (due to set -e).
Now, to understand this in the context of a 'script', use this simple script:
#!/bin/bash
# set -e
lsd
ls
If you run it as is, you'll get the directory listing from the ls on the last line. If you uncomment the set -e and run again, you won't see the directory listing as bash stops processing once it encounters the error from lsd.
set -e The set -e option instructs bash to immediately exit if any command [1] has a non-zero exit status. You wouldn't want to set this for your command-line shell, but in a script it's massively helpful. In all widely used general-purpose programming languages, an unhandled runtime error - whether that's a thrown exception in Java, or a segmentation fault in C, or a syntax error in Python - immediately halts execution of the program; subsequent lines are not executed.
By default, bash does not do this. This default behavior is exactly what you want if you are using bash on the command line
you don't want a typo to log you out! But in a script, you really want the opposite.
If one line in a script fails, but the last line succeeds, the whole script has a successful exit code. That makes it very easy to miss the error.
Again, what you want when using bash as your command-line shell and using it in scripts are at odds here. Being intolerant of errors is a lot better in scripts, and that's what set -e gives you.
copied from : https://gist.github.com/mohanpedala/1e2ff5661761d3abd0385e8223e16425
this may help you .
Script 1: without setting -e
#!/bin/bash
decho "hi"
echo "hello"
This will throw error in decho and program continuous to next line
Script 2: With setting -e
#!/bin/bash
set -e
decho "hi"
echo "hello"
# Up to decho "hi" shell will process and program exit, it will not proceed further
It stops execution of a script if a command fails.
A notable exception is an if statement. eg:
set -e
false
echo never executed
set -e
if false; then
echo never executed
fi
echo executed
false
echo never executed
cat a.sh
#! /bin/bash
#going forward report subshell or command exit value if errors
#set -e
(cat b.txt)
echo "hi"
./a.sh; echo $?
cat: b.txt: No such file or directory
hi
0
with set -e commented out we see that echo "hi" exit status being reported and hi is printed.
cat a.sh
#! /bin/bash
#going forward report subshell or command exit value if errors
set -e
(cat b.txt)
echo "hi"
./a.sh; echo $?
cat: b.txt: No such file or directory
1
Now we see b.txt error being reported instead and no hi printed.
So default behaviour of shell script is to ignore command errors and continue processing and report exit status of last command. If you want to exit on error and report its status we can use -e option.

Abort bash script if git pull fails [duplicate]

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

Bash - break conditional clause if one of the statements return error code != 0

I have the following bash script which runs on my CI and intends to run my code on a physical MacOS and on several docker Linux images:
if [[ "$OS_NAME" == "mac_os" ]]; then
make all;
run_test1;
run_test2;
make install;
else
docker exec -i my_docker_image bash -c "make all";
docker exec -i my_docker_image bash -c "run_test1";
docker exec -i my_docker_image bash -c "run_test2";
docker exec -i my_docker_image bash -c "make install";
fi
If the tests fail (run_test1 or run_test2) they return error code 1. If they pass they return error code 0.
The whole script runs with set -e so whenever it sees exit code other than 0 it stops and fails the entire build.
The problem is that currently, when run_test1 and run_test2 are inside the conditional clause - when they fail and return error code 1 the conditional clause doesn't break and the build succeeds although tests didn't pass.
So I have 2 questions:
How to break the conditional clause if one of the commands return error code other than 0?
How to break the conditional clause in such a way that the entire clause will return an error code (so the whole build will fail)?
Your code should work as expected, let's demonstrate this:
#!/usr/bin/env bash
set -e
var="test"
if [[ $var = test ]]; then
echo "Hello"
cat non_existing_file &> /dev/null
echo "World"
else
echo "Else hello"
cat non_existing file &> /dev/null
fi
echo I am done
This will output only "Hello", as expected. If it works differently for you, it means you didn't provide enough code. Let's try to change the code above and show some examples when set -e is ignored, just like in your case:
Quoting Bash Reference manual:
If a compound command or shell function executes in a context where -e
is being ignored, none of the commands executed within the compound
command or function body will be affected by the -e setting, even if
-e is set and a command returns a failure status.
Now let's quote the same manual and see some cases where -e is ignored:
The shell does not exit if the command that fails is part of the
command list immediately following a while or until keyword, part of
the test in an if statement, part of any command executed in a && or
|| list except the command following the final && or ||, any command
in a pipeline but the last, or if the command’s return status is being
inverted with !.
From this we can see that, for example, if you had the code above in a function and tested that function with if, set -e would be ignored:
#!/usr/bin/env bash
set -e
f() {
var="test"
if [[ $var = test ]]; then
echo "Hello"
cat non_existing_file &> /dev/null
echo "World"
else
echo "Else hello"
cat non_existing file &> /dev/null
fi
}
if f; then echo "Function OK!"; fi
echo I am done
Function f is executed in a context where set -e is being ignored (if statement), meaning that set -e doesn't affect any of the commands executed within this function. This code outputs:
Hello
World
Function OK!
I am done
The same rules apply when you execute the function in a && or || list. If you change the line if f; then echo "Function OK!"; fi to f && echo "Function OK", you will get the same output. I believe the latter could be your case.
Even so, your second question can be solved easily by adding || exit:
run_test1 || exit 1;
run_test2 || exit 1;
Your first question is trivial if you are inside a function for example. Then you can simply return. Or inside a loop, then you can break. If you are not, breaking out of the conditional clause is not that easy. Take a look at this answer.
set -e can be a surprising thing as it is being ignored in many cases. Use it with care and be aware of these cases.

Bash: redirect to screen or /dev/null depending on flag

I'm trying to come up with a way script to pass a silent flag in a bash so that all output will be directed to /dev/null if it is present and to the screen if it is not.
An MWE of my script would be:
#!/bin/bash
# Check if silent flag is on.
if [ $2 = "-s" ]; then
echo "Silent mode."
# Non-working line.
out_var = "to screen"
else
echo $1
# Non-working line.
out_var = "/dev/null"
fi
command1 > out_var
command2 > out_var
echo "End."
I call the script with two variables, the first one is irrelevant and the second one ($2) is the actual silent flag (-s):
./myscript.sh first_variable -s
Obviously the out_var lines don't work, but they give an idea of what I want: a way to direct the output of command1 and command2 to either the screen or to /dev/null depending on -s being present or not.
How could I do this?
You can use the naked exec command to redirect the current program without starting a new one.
Hence, a -s flag could be processed with something like:
if [[ "$1" == "-s" ]] ; then
exec >/dev/null 2>&1
fi
The following complete script shows how to do it:
#!/bin/bash
echo XYZZY
if [[ "$1" == "-s" ]] ; then
exec >/dev/null 2>&1
fi
echo PLUGH
If you run it with -s, you get XYZZY but no PLUGH output (well, technically, you do get PLUGH output but it's sent to the /dev/null bit bucket).
If you run it without -s, you get both lines.
The before and after echo statements show that exec is acting as described, simply changing redirection for the current program rather than attempting to re-execute it.
As an aside, I've assumed you meant "to screen" to be "to the current standard output", which may or may not be the actual terminal device (for example if it's already been redirected to somewhere else). If you do want the actual terminal device, it can still be done (using /dev/tty for example) but that would be an unusual requirement.
There are lots of things that could be wrong with your script; I won't attempt to guess since you didn't post any actual output or errors.
However, there are a couple of things that can help:
You need to figure out where your output is really going. Standard output and standard error are two different things, and redirecting one doesn't necessarily redirect the other.
In Bash, you can send output to /dev/stdout or /dev/stderr, so you might want to try something like:
# Send standard output to the tty/pty, or wherever stdout is currently going.
cmd > /dev/stdout
# Do the same thing, but with standard error instead.
cmd > /dev/stderr
Redirect standard error to standard output, and then send standard output to /dev/null. Order matters here.
cmd 2>&1 > /dev/null
There may be other problems with your script, too, but for issues with Bash shell redirections the GNU Bash manual is the canonical source of information. Hope it helps!
If you don't want to redirect all output from your script, you can use eval. For example:
$ fd=1
$ eval "echo hi >$a" >/dev/null
$ fd=2
$ eval "echo hi >$a" >/dev/null
hi
Make sure you use double quotes so that the variable is replaced before eval evaluates it.
In your case, you just needed to change out_var = "to screen" to out_var = "/dev/tty". And use it like this command1 > $out_var (see the '$' you are lacking)
I implemented it like this
# Set debug flag as desired
DEBUG=1
# DEBUG=0
if [ "$DEBUG" -eq "1" ]; then
OUT='/dev/tty'
else
OUT='/dev/null'
fi
# actual script use commands like this
command > $OUT 2>&1
# or like this if you need
command 2> $OUT
Of course you can also set the debug mode from a cli option, see How do I parse command line arguments in Bash?
And you can have multiple debug or verbose levels like this
# Set VERBOSE level as desired
# VERBOSE=0
VERBOSE=1
# VERBOSE=2
VERBOSE1='/dev/null'
VERBOSE2='/dev/null'
if [ "$VERBOSE" -gte 1 ]; then
VERBOSE1='/dev/tty'
fi
if [ "$VERBOSE" -gte 2 ]; then
VERBOSE2='/dev/tty'
fi
# actual script use commands like this
command > $VERBOSE1 2>&1
# or like this if you need
command 2> $VERBOSE2

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