I've the below code:
#!/bin/bash
. ~/.bash_profile
dt=$(date +"%Y.%m.%d")
if [[ "$#" -eq '0' ]] || [[ "$#" -eq '1' ]]
then
echo -e "Not correct usage"
exit 1
fi
tar zvxf $SHARE/*.gz -C $SHARE/landing/
sleep 3
ops () {
//
some sets of command
//
}
while read -r line
do
if [[ "$1" == "A" ]] || [[ "$1" == "B" ]] || [[ "$1" == "C" ]] && [[ "$2" =~ "$line" ]] || [[ "$2" == "ALL" ]]
then
ops
fi
done < $SHARE/landing/dir/ApprovedList."$1"
When i run the script, i can see that it's able to untar the .gz file and place it into the folder :$SHARE/landing/
But i guess it's not able to read the file and perform the operations inside the ops function, below is the last line of output i'm getting after running the script in interactive mode:
+ read -r line
Any help is most welcome!!!
Please show the input format, the argument format, and some explanation of those. In the meantime, tweaked for readability and error handling - edit to taste. YMMV.
#!/bin/bash
. ~/.bash_profile
ops () { # do some stuff
: some sets of commands ...
}
die() {
printf "%s\n\n Use: $0 x y z ...\n\n" "$1" >&2
kill -term $$ # exit in function behaves like return
}
# dt=$(date +"%Y.%m.%d") # unused
case "$#" in
0|1) die "Insufficient arguments" ;;
esac
tar zvxf "$SHARE"/*.gz -C "$SHARE/landing/" || die "tar failed"
sleep 3
infile="$SHARE/landing/dir/ApprovedList.$1"
[[ -e "$infile" ]] || die "$infile does not exist"
[[ -r "$infile" ]] || die "$infile is nor readable by $0 as $LOGNAME"
while read -r line
do case "$1" in
A|B|C) case "$2" in
*"$line"*|ALL) ops ;;
*) : data does not match, skipping ;;
esac ;;
*) die "Invalid arg1 '$1'";;
esac
done < "$infile"
Notes:
If you require exactly 2 arguments, then let's check exactly that:
die() {
printf "%s\n\n Use: $0 x y\n\n" "$1" >&2
kill -term $$ # exit in function behaves like return
}
and
case "$#" in
2) ;;
*) die "Incorrect # of arguments" ;;
esac
Also, better than the kill - add a trap at the top:
trap 'echo >&2 "ERROR in $0($BASH_SOURCE) at line $LINENO: [$BASH_COMMAND]"; exit $LINENO;' ERR
and use a literal error return in the function.
die() {
printf "%s\n\n Use: $0 x y\n\n" "$1" >&2
return 1
}
The check (except for [[ "$2" =~ "$line" ]])
if [[ "$1" == "A" ]] || [[ "$1" == "B" ]] || [[ "$1" == "C" ]] && [[ "$2" =~ "$line" ]] || [[ "$2" == "ALL" ]]
doesn't change inside the while-loop. So better check once before entering the while-loop.
So now you want to perform ops for each line of $SHARE/landing/dir/ApprovedList."$1".
You can use
xargs -a "$SHARE/landing/dir/ApprovedList.$1" -L 1 ops
EDIT:
When you have a simple check to perform for each line, you can move this check into the ops function.
First save $2 before entering the function:
to_be_checked="$2"
...
ops() {
[[ "$0" =~ "${to_be_checked}" ]] && return
am not expert on bash script and am looking help on. I would like to find a way at the end from the while loop condition that the script can be executed unless one option ([-1|-2|-3]) has been chosen OR none of them.
What the best way to do? I have absolutely no idea how to.
Many Thanks.
#!/bin/bash
echo " $0 [-e <option_e>] [-f <option_f>] [-1|-2|-3] [user#]fqdn"
OPTION1=""
OPTION2=""
OPTION3=""
while (( "$#" )); do
if [ "$1" == "-1" ]; then
OPTION1=1
elif [ "$1" == "-2" ]; then
OPTION2=1
elif [ "$1" == "-3" ]; then
OPTION3=1
fi
shift
done
I forgot to mention. this is a part of the script. further, there are several conditions that can conflict if there more then 2 options chosen.
EDIT: the valid selections either exactly one option or zero, but not two or more!
thank you SamuelKirschner -
I did to add [[ -n $ALL_OPTS ]] && then it works ! I am happy now.
#!/bin/bash
OPTION1=""
OPTION2=""
OPTION3=""
while (( "$#" )); do
if [ "$1" == "-1" ]; then
OPTION1=1
elif [ "$1" == "-2" ]; then
OPTION2=1
elif [ "$1" == "-3" ]; then
OPTION3=1
fi
shift
done
ALL_OPTS="$OPTION1$OPTION2$OPTION3";
echo $ALL_OPTS
if [[ -n $ALL_OPTS ]] && [[ $ALL_OPTS -ge 2 ]];then
echo 'Please provide a maximum of one of the options [-1|-2|-3]' 1>&2
exit 1
fi
You can simply test if all of the OPTION-variables concated have the wrong length with ALL_OPTS="$OPTION1$OPTION2$OPTION3"; test ${#ALL_OPTS} -ge 2 and exit. Where "$OPTION1$OPTION2$OPTION3" is just all of the variables written next to each other, therefor it is "", "1", "11" or "111".
#!/bin/bash
echo " $0 [-e <option_e>] [-f <option_f>] [-1|-2|-3] [user#]fqdn"
OPTION1=""
OPTION2=""
OPTION3=""
while (( "$#" )); do
if [ "$1" == "-1" ]; then
OPTION1=1
elif [ "$1" == "-2" ]; then
OPTION2=1
elif [ "$1" == "-3" ]; then
OPTION3=1
fi
shift
done
ALL_OPTS="$OPTION1$OPTION2$OPTION3";
if test ${#ALL_OPTS} -ge 2; then
echo 'Please provide a maximum of one of the options [-1|-2|-3]' 1>&2
exit 1
fi
From man bash
${#parameter}
Parameter length. The length in characters of the value of parameter is substituted. [...]
Edit: I messed up the condition quite a bit. (original answer was test -z "$OPTION1$OPTION2$OPTION3")
Keeping a count of options might be a possibility. Something like this, using getopts:
#!/usr/bin/env bash
echo "${0##*/} [-e <option_e>] [-f <option_f>] [-1|-2|-3] [user#]fqdn"
count=0
while getopts e:f:123 opt; do
case "$opt" in
e) opt_e="$OPTARG" ;;
f) opt_f="$OPTARG" ;;
1|2|3) declare opt_$opt=true; ((count++)) ;;
esac
done
shift $((OPTIND-1))
# Fail if our counter is too high
((count>1)) && printf 'ERROR: only one digit option allowed.\n' >&2 && exit 1
echo "done"
Alternately, you could keep the numeric options in a variable which you could check using globs:
#!/usr/bin/env bash
echo "${0##*/} [-e <option_e>] [-f <option_f>] [-1|-2|-3] [user#]fqdn"
nopt=""
while getopts e:f:123 opt; do
case "$opt" in
e|f) declare opt_$opt="$OPTARG" ;;
1|2|3) nopt="$nopt$opt" ;;
esac
done
shift $((OPTIND-1))
# Fail if we collected too many digits
((${#nopt}>1)) && printf 'ERROR: only one digit option allowed.\n' >&2 && exit 1
echo "done"
Then, you could switch functionality based on the value of $nopt.
For some reason, I can't figure out how to test truth in bash:
#!/bin/bash
FORCE_DELETE=""
BE_VERBOSE=""
OPTIND=1
while getopts ":fv" FLAG "$#" ; do
if [[ "$FLAG" == "f" ]] ; then
FORCE_DELETE="true"
fi
if [[ "$VALUE" == "v" ]] ; then
BE_VERBOSE="true"
fi
if [[ "$FLAG" == "?" ]] ; then
echo "Usage: $0 [-fv] file ..."
exit 1
fi
done
shift `expr $OPTIND - 1`
if [[ "$FORCE_DELETE" == "true" && "BE_VERBOSE" == "true" ]] ; then
echo "FORCE_DELETE AND BE_VERBOSE $#"
elif [[ "$FORCE_DELETE" == "true" ]] ; then
echo "FORCE_DELETE $#"
elif [[ "$BE_VERBOSE" == "true" ]] ; then
echo "BE_VERBOSE $#"
else
echo "$#"
fi
exit 0
Transcript:
$ test a b
a b
$ test -f a b
FORCE_DELETE a b
$ test -v a b
a b
$ test -fv a b
FORCE_DELETE a b
Why does my bash script respond to the -f flag but not the -v flag?
Most likely a typo :
[[ "$VALUE" == "v" ]],
this should be
[[ "$FLAG" == "v" ]]
You specifically ask about testing true/false. These are built in to the language rather than using strings, and you don't need the [[ test. Here is how I would write this:
#!/bin/bash
force_delete=false # Don't use UPPERCASE
be_verbose=false # they could collide with reserved variables
# OPTIND does not need to be initialised
while getopts :fv flag
do
# appears one of your if statements is incorrect
# a case is often used with getopts
case $flag in
f) force_delete=true
;;
v) be_verbose=true
;;
\?) echo "Usage: $0 [-fv] file ..."
exit 1
;;
esac
done
shift $((OPTIND-1)) # don't create a child process for simple arithmetic
if $force_delete && $be_verbose
then
echo "force_delete AND be_verbose $#"
elif $force_delete
then
echo "force_delete $#"
elif $be_verbose
then
echo "be_verbose $#"
else
echo "$#"
fi
# Bash exits 0 by default
I'm writing a shell script and need to check that a terminal app has been installed. I want to use a TRY/CATCH command to do this unless there is a neater way.
Is there a TRY CATCH command in Bash?
No.
Bash doesn't have as many luxuries as one can find in many programming languages.
There is no try/catch in bash; however, one can achieve similar behavior using && or ||.
Using ||:
if command1 fails then command2 runs as follows
command1 || command2
Similarly, using &&, command2 will run if command1 is successful
The closest approximation of try/catch is as follows
{ # try
command1 &&
#save your output
} || { # catch
# save log for exception
}
Also bash contains some error handling mechanisms, as well
set -e
it stops your script if any simple command fails.
And also why not if...else. It is your best friend.
Based on some answers I found here, I made myself a small helper file to source for my projects:
trycatch.sh
#!/bin/bash
function try()
{
[[ $- = *e* ]]; SAVED_OPT_E=$?
set +e
}
function throw()
{
exit $1
}
function catch()
{
export ex_code=$?
(( $SAVED_OPT_E )) && set +e
return $ex_code
}
function throwErrors()
{
set -e
}
function ignoreErrors()
{
set +e
}
here is an example how it looks in use:
#!/bin/bash
export AnException=100
export AnotherException=101
# start with a try
try
( # open a subshell !!!
echo "do something"
[ someErrorCondition ] && throw $AnException
echo "do something more"
executeCommandThatMightFail || throw $AnotherException
throwErrors # automaticatly end the try block, if command-result is non-null
echo "now on to something completely different"
executeCommandThatMightFail
echo "it's a wonder we came so far"
executeCommandThatFailsForSure || true # ignore a single failing command
ignoreErrors # ignore failures of commands until further notice
executeCommand1ThatFailsForSure
local result = $(executeCommand2ThatFailsForSure)
[ result != "expected error" ] && throw $AnException # ok, if it's not an expected error, we want to bail out!
executeCommand3ThatFailsForSure
# make sure to clear $ex_code, otherwise catch * will run
# echo "finished" does the trick for this example
echo "finished"
)
# directly after closing the subshell you need to connect a group to the catch using ||
catch || {
# now you can handle
case $ex_code in
$AnException)
echo "AnException was thrown"
;;
$AnotherException)
echo "AnotherException was thrown"
;;
*)
echo "An unexpected exception was thrown"
throw $ex_code # you can rethrow the "exception" causing the script to exit if not caught
;;
esac
}
I've developed an almost flawless try & catch implementation in bash, that allows you to write code like:
try
echo 'Hello'
false
echo 'This will not be displayed'
catch
echo "Error in $__EXCEPTION_SOURCE__ at line: $__EXCEPTION_LINE__!"
You can even nest the try-catch blocks inside themselves!
try {
echo 'Hello'
try {
echo 'Nested Hello'
false
echo 'This will not execute'
} catch {
echo "Nested Caught (# $__EXCEPTION_LINE__)"
}
false
echo 'This will not execute too'
} catch {
echo "Error in $__EXCEPTION_SOURCE__ at line: $__EXCEPTION_LINE__!"
}
The code is a part of my bash boilerplate/framework. It further extends the idea of try & catch with things like error handling with backtrace and exceptions (plus some other nice features).
Here's the code that's responsible just for try & catch:
set -o pipefail
shopt -s expand_aliases
declare -ig __oo__insideTryCatch=0
# if try-catch is nested, then set +e before so the parent handler doesn't catch us
alias try="[[ \$__oo__insideTryCatch -gt 0 ]] && set +e;
__oo__insideTryCatch+=1; ( set -e;
trap \"Exception.Capture \${LINENO}; \" ERR;"
alias catch=" ); Exception.Extract \$? || "
Exception.Capture() {
local script="${BASH_SOURCE[1]#./}"
if [[ ! -f /tmp/stored_exception_source ]]; then
echo "$script" > /tmp/stored_exception_source
fi
if [[ ! -f /tmp/stored_exception_line ]]; then
echo "$1" > /tmp/stored_exception_line
fi
return 0
}
Exception.Extract() {
if [[ $__oo__insideTryCatch -gt 1 ]]
then
set -e
fi
__oo__insideTryCatch+=-1
__EXCEPTION_CATCH__=( $(Exception.GetLastException) )
local retVal=$1
if [[ $retVal -gt 0 ]]
then
# BACKWARDS COMPATIBILE WAY:
# export __EXCEPTION_SOURCE__="${__EXCEPTION_CATCH__[(${#__EXCEPTION_CATCH__[#]}-1)]}"
# export __EXCEPTION_LINE__="${__EXCEPTION_CATCH__[(${#__EXCEPTION_CATCH__[#]}-2)]}"
export __EXCEPTION_SOURCE__="${__EXCEPTION_CATCH__[-1]}"
export __EXCEPTION_LINE__="${__EXCEPTION_CATCH__[-2]}"
export __EXCEPTION__="${__EXCEPTION_CATCH__[#]:0:(${#__EXCEPTION_CATCH__[#]} - 2)}"
return 1 # so that we may continue with a "catch"
fi
}
Exception.GetLastException() {
if [[ -f /tmp/stored_exception ]] && [[ -f /tmp/stored_exception_line ]] && [[ -f /tmp/stored_exception_source ]]
then
cat /tmp/stored_exception
cat /tmp/stored_exception_line
cat /tmp/stored_exception_source
else
echo -e " \n${BASH_LINENO[1]}\n${BASH_SOURCE[2]#./}"
fi
rm -f /tmp/stored_exception /tmp/stored_exception_line /tmp/stored_exception_source
return 0
}
Feel free to use, fork and contribute - it's on GitHub.
bash does not abort the running execution in case something detects an error state (unless you set the -e flag). Programming languages which offer try/catch do this in order to inhibit a "bailing out" because of this special situation (hence typically called "exception").
In the bash, instead, only the command in question will exit with an exit code greater than 0, indicating that error state. You can check for that of course, but since there is no automatic bailing out of anything, a try/catch does not make sense. It is just lacking that context.
You can, however, simulate a bailing out by using sub shells which can terminate at a point you decide:
(
echo "Do one thing"
echo "Do another thing"
if some_condition
then
exit 3 # <-- this is our simulated bailing out
fi
echo "Do yet another thing"
echo "And do a last thing"
) # <-- here we arrive after the simulated bailing out, and $? will be 3 (exit code)
if [ $? = 3 ]
then
echo "Bail out detected"
fi
Instead of that some_condition with an if you also can just try a command, and in case it fails (has an exit code greater than 0), bail out:
(
echo "Do one thing"
echo "Do another thing"
some_command || exit 3
echo "Do yet another thing"
echo "And do a last thing"
)
...
Unfortunately, using this technique you are restricted to 255 different exit codes (1..255) and no decent exception objects can be used.
If you need more information to pass along with your simulated exception, you can use the stdout of the subshells, but that is a bit complicated and maybe another question ;-)
Using the above mentioned -e flag to the shell you can even strip that explicit exit statement:
(
set -e
echo "Do one thing"
echo "Do another thing"
some_command
echo "Do yet another thing"
echo "And do a last thing"
)
...
You can use trap:
try { block A } catch { block B } finally { block C }
translates to:
(
set -Ee
function _catch {
block B
exit 0 # optional; use if you don't want to propagate (rethrow) error to outer shell
}
function _finally {
block C
}
trap _catch ERR
trap _finally EXIT
block A
)
There are so many similar solutions which probably work. Below is a simple and working way to accomplish try/catch, with explanation in the comments.
#!/bin/bash
function a() {
# do some stuff here
}
function b() {
# do more stuff here
}
# this subshell is a scope of try
# try
(
# this flag will make to exit from current subshell on any error
# inside it (all functions run inside will also break on any error)
set -e
a
b
# do more stuff here
)
# and here we catch errors
# catch
errorCode=$?
if [ $errorCode -ne 0 ]; then
echo "We have an error"
# We exit the all script with the same error, if you don't want to
# exit it and continue, just delete this line.
exit $errorCode
fi
As everybody says, bash doesn't have a proper language-supported try/catch syntax. You can launch bash with the -e argument or use set -e inside the script to abort the entire bash process if any command has a non-zero exit code. (You can also set +e to temporarily allow failing commands.)
So, one technique to simulate a try/catch block is to launch a sub-process to do the work with -e enabled. Then in the main process, check the return code of the sub-process.
Bash supports heredoc strings, so you don't have to write two separate files to handle this. In the below example, the TRY heredoc will run in a separate bash instance, with -e enabled, so the sub-process will crash if any command returns a non-zero exit code. Then, back in the main process, we can check the return code to handle a catch block.
#!/bin/bash
set +e
bash -e <<TRY
echo hello
cd /does/not/exist
echo world
TRY
if [ $? -ne 0 ]; then
echo caught exception
fi
It's not a proper language-supported try/catch block, but it may scratch a similar itch for you.
You can do:
#!/bin/bash
if <command> ; then # TRY
<do-whatever-you-want>
else # CATCH
echo 'Exception'
<do-whatever-you-want>
fi
I use something like this:
YOUR COMMAND HERE
EXITCODE=$?
if [ "$EXITCODE" -ne "0" ]; then
#this is the catch part
echo "uh oh"
exit $EXITCODE
fi
this just checks the exit code of the command and compares it to zero
(which indicates the command ran successfully)
And you have traps http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_12_02.html which is not the same, but other technique you can use for this purpose
Assuming the terminal app in question is named 'app' (and you expect it to be in your $PATH):
if [[ ! `which app` ]]; then
# run code if app not installed
else
# run code if app is installed
fi
To piggyback Sean Mayo's answer, you can do like this
function check {
EXITCODE=$?
if [ "$EXITCODE" -ne "0" ]; then
#this is the catch part
echo "uh oh"
exit $EXITCODE
fi
}
YOUR COMMAND HERE
check
YOUR COMMAND HERE
check
YOUR COMMAND HERE
check
YOUR COMMAND HERE
check
It works well
I can recommend this in "bash -ue" mode:
set -ue
false && RET=$? || RET=$?
echo "expecting 1, got ${RET}"
true && RET=$? || RET=$?
echo "expecting 0, got ${RET}"
echo "test try...catch"
false && RET=$? || RET=$?
if [ ${RET} -ne 0 ]; then
echo "caught error ${RET}"
fi
echo "beware, using '||' before '&&' fails"
echo " -> memory aid: [A]nd before [O]r in the alphabet"
false || RET=$? && RET=$?
echo "expecting 1, got ${RET}"
true || RET=$? && RET=$?
echo "expecting 0, got ${RET}"
A very simple thing I use:
try() {
"$#" || (e=$?; echo "$#" > /dev/stderr; exit $e)
}
Below is an complete copy of the simplified script used in my other answer. Beyond additional error checking, there is an alias which allows the user to change the name of an existing alias. The syntax is given below. If the new_alias parameter is omitted, then the alias is removed.
ChangeAlias old_alias [new_alias]
The complete script is given below.
common.GetAlias() {
local "oldname=${1:-0}"
if [[ $oldname =~ ^[0-9]+$ && oldname+1 -lt ${#FUNCNAME[#]} ]]; then
oldname="${FUNCNAME[oldname + 1]}"
fi
name="common_${oldname#common.}"
echo "${!name:-$oldname}"
}
common.Alias() {
if [[ $# -ne 2 || -z $1 || -z $2 ]]; then
echo "$(common.GetAlias): The must be only two parameters of nonzero length" >&2
return 1;
fi
eval "alias $1='$2'"
local "f=${2##*common.}"
f="${f%%;*}"
local "v=common_$f"
f="common.$f"
if [[ -n ${!v:-} ]]; then
echo "$(common.GetAlias): $1: Function \`$f' already paired with name \`${!v}'" >&2
return 1;
fi
shopt -s expand_aliases
eval "$v=\"$1\""
}
common.ChangeAlias() {
if [[ $# -lt 1 || $# -gt 2 ]]; then
echo "usage: $(common.GetAlias) old_name [new_name]" >&2
return "1"
elif ! alias "$1" &>"/dev/null"; then
echo "$(common.GetAlias): $1: Name not found" >&2
return 1;
fi
local "s=$(alias "$1")"
s="${s#alias $1=\'}"
s="${s%\'}"
local "f=${s##*common.}"
f="${f%%;*}"
local "v=common_$f"
f="common.$f"
if [[ ${!v:-} != "$1" ]]; then
echo "$(common.GetAlias): $1: Name not paired with a function \`$f'" >&2
return 1;
elif [[ $# -gt 1 ]]; then
eval "alias $2='$s'"
eval "$v=\"$2\""
else
unset "$v"
fi
unalias "$1"
}
common.Alias exception 'common.Exception'
common.Alias throw 'common.Throw'
common.Alias try '{ if common.Try; then'
common.Alias yrt 'common.EchoExitStatus; fi; common.yrT; }'
common.Alias catch '{ while common.Catch'
common.Alias hctac 'common.hctaC -r; done; common.hctaC; }'
common.Alias finally '{ if common.Finally; then'
common.Alias yllanif 'fi; common.yllaniF; }'
common.Alias caught 'common.Caught'
common.Alias EchoExitStatus 'common.EchoExitStatus'
common.Alias EnableThrowOnError 'common.EnableThrowOnError'
common.Alias DisableThrowOnError 'common.DisableThrowOnError'
common.Alias GetStatus 'common.GetStatus'
common.Alias SetStatus 'common.SetStatus'
common.Alias GetMessage 'common.GetMessage'
common.Alias MessageCount 'common.MessageCount'
common.Alias CopyMessages 'common.CopyMessages'
common.Alias TryCatchFinally 'common.TryCatchFinally'
common.Alias DefaultErrHandler 'common.DefaultErrHandler'
common.Alias DefaultUnhandled 'common.DefaultUnhandled'
common.Alias CallStack 'common.CallStack'
common.Alias ChangeAlias 'common.ChangeAlias'
common.Alias TryCatchFinallyAlias 'common.Alias'
common.CallStack() {
local -i "i" "j" "k" "subshell=${2:-0}" "wi" "wl" "wn"
local "format= %*s %*s %-*s %s\n" "name"
eval local "lineno=('' ${BASH_LINENO[#]})"
for (( i=${1:-0},j=wi=wl=wn=0; i<${#FUNCNAME[#]}; ++i,++j )); do
name="$(common.GetAlias "$i")"
let "wi = ${#j} > wi ? wi = ${#j} : wi"
let "wl = ${#lineno[i]} > wl ? wl = ${#lineno[i]} : wl"
let "wn = ${#name} > wn ? wn = ${#name} : wn"
done
for (( i=${1:-0},j=0; i<${#FUNCNAME[#]}; ++i,++j )); do
! let "k = ${#FUNCNAME[#]} - i - 1"
name="$(common.GetAlias "$i")"
printf "$format" "$wi" "$j" "$wl" "${lineno[i]}" "$wn" "$name" "${BASH_SOURCE[i]}"
done
}
common.Echo() {
[[ $common_options != *d* ]] || echo "$#" >"$common_file"
}
common.DefaultErrHandler() {
echo "Orginal Status: $common_status"
echo "Exception Type: ERR"
}
common.Exception() {
common.TryCatchFinallyVerify || return
if [[ $# -eq 0 ]]; then
echo "$(common.GetAlias): At least one parameter is required" >&2
return "1"
elif [[ ${#1} -gt 16 || -n ${1%%[0-9]*} || 10#$1 -lt 1 || 10#$1 -gt 255 ]]; then
echo "$(common.GetAlias): $1: First parameter was not an integer between 1 and 255" >&2
return "1"
fi
let "common_status = 10#$1"
shift
common_messages=()
for message in "$#"; do
common_messages+=("$message")
done
if [[ $common_options == *c* ]]; then
echo "Call Stack:" >"$common_fifo"
common.CallStack "2" >"$common_fifo"
fi
}
common.Throw() {
common.TryCatchFinallyVerify || return
local "message"
if ! common.TryCatchFinallyExists; then
echo "$(common.GetAlias): No Try-Catch-Finally exists" >&2
return "1"
elif [[ $# -eq 0 && common_status -eq 0 ]]; then
echo "$(common.GetAlias): No previous unhandled exception" >&2
return "1"
elif [[ $# -gt 0 && ( ${#1} -gt 16 || -n ${1%%[0-9]*} || 10#$1 -lt 1 || 10#$1 -gt 255 ) ]]; then
echo "$(common.GetAlias): $1: First parameter was not an integer between 1 and 255" >&2
return "1"
fi
common.Echo -n "In Throw ?=$common_status "
common.Echo "try=$common_trySubshell subshell=$BASH_SUBSHELL #=$#"
if [[ $common_options == *k* ]]; then
common.CallStack "2" >"$common_file"
fi
if [[ $# -gt 0 ]]; then
let "common_status = 10#$1"
shift
for message in "$#"; do
echo "$message" >"$common_fifo"
done
if [[ $common_options == *c* ]]; then
echo "Call Stack:" >"$common_fifo"
common.CallStack "2" >"$common_fifo"
fi
elif [[ ${#common_messages[#]} -gt 0 ]]; then
for message in "${common_messages[#]}"; do
echo "$message" >"$common_fifo"
done
fi
chmod "0400" "$common_fifo"
common.Echo "Still in Throw $=$common_status subshell=$BASH_SUBSHELL #=$# -=$-"
exit "$common_status"
}
common.ErrHandler() {
common_status=$?
trap ERR
common.Echo -n "In ErrHandler ?=$common_status debug=$common_options "
common.Echo "try=$common_trySubshell subshell=$BASH_SUBSHELL order=$common_order"
if [[ -w "$common_fifo" ]]; then
if [[ $common_options != *e* ]]; then
common.Echo "ErrHandler is ignoring"
common_status="0"
return "$common_status" # value is ignored
fi
if [[ $common_options == *k* ]]; then
common.CallStack "2" >"$common_file"
fi
common.Echo "Calling ${common_errHandler:-}"
eval "${common_errHandler:-} \"${BASH_LINENO[0]}\" \"${BASH_SOURCE[1]}\" \"${FUNCNAME[1]}\" >$common_fifo <$common_fifo"
if [[ $common_options == *c* ]]; then
echo "Call Stack:" >"$common_fifo"
common.CallStack "2" >"$common_fifo"
fi
chmod "0400" "$common_fifo"
fi
common.Echo "Still in ErrHandler $=$common_status subshell=$BASH_SUBSHELL -=$-"
if [[ common_trySubshell -eq BASH_SUBSHELL ]]; then
return "$common_status" # value is ignored
else
exit "$common_status"
fi
}
common.Token() {
local "name"
case $1 in
b) name="before";;
t) name="$common_Try";;
y) name="$common_yrT";;
c) name="$common_Catch";;
h) name="$common_hctaC";;
f) name="$common_yllaniF";;
l) name="$common_Finally";;
*) name="unknown";;
esac
echo "$name"
}
common.TryCatchFinallyNext() {
common.ShellInit
local "previous=$common_order" "errmsg"
common_order="$2"
if [[ $previous != $1 ]]; then
errmsg="${BASH_SOURCE[2]}: line ${BASH_LINENO[1]}: syntax error_near unexpected token \`$(common.Token "$2")'"
echo "$errmsg" >&2
[[ /dev/fd/2 -ef $common_file ]] || echo "$errmsg" >"$common_file"
kill -s INT 0
return "1"
fi
}
common.ShellInit() {
if [[ common_initSubshell -ne BASH_SUBSHELL ]]; then
common_initSubshell="$BASH_SUBSHELL"
common_order="b"
fi
}
common.Try() {
common.TryCatchFinallyVerify || return
common.TryCatchFinallyNext "[byhl]" "t" || return
common_status="0"
common_subshell="$common_trySubshell"
common_trySubshell="$BASH_SUBSHELL"
common_messages=()
common.Echo "-------------> Setting try=$common_trySubshell at subshell=$BASH_SUBSHELL"
}
common.yrT() {
local "status=$?"
common.TryCatchFinallyVerify || return
common.TryCatchFinallyNext "[t]" "y" || return
common.Echo -n "Entered yrT ?=$status status=$common_status "
common.Echo "try=$common_trySubshell subshell=$BASH_SUBSHELL"
if [[ common_status -ne 0 ]]; then
common.Echo "Build message array. ?=$common_status, subshell=$BASH_SUBSHELL"
local "message=" "eof=TRY_CATCH_FINALLY_END_OF_MESSAGES_$RANDOM"
chmod "0600" "$common_fifo"
echo "$eof" >"$common_fifo"
common_messages=()
while read "message"; do
common.Echo "----> $message"
[[ $message != *$eof ]] || break
common_messages+=("$message")
done <"$common_fifo"
fi
common.Echo "In ytT status=$common_status"
common_trySubshell="$common_subshell"
}
common.Catch() {
common.TryCatchFinallyVerify || return
common.TryCatchFinallyNext "[yh]" "c" || return
[[ common_status -ne 0 ]] || return "1"
local "parameter" "pattern" "value"
local "toggle=true" "compare=p" "options=$-"
local -i "i=-1" "status=0"
set -f
for parameter in "$#"; do
if "$toggle"; then
toggle="false"
if [[ $parameter =~ ^-[notepr]$ ]]; then
compare="${parameter#-}"
continue
fi
fi
toggle="true"
while "true"; do
eval local "patterns=($parameter)"
if [[ ${#patterns[#]} -gt 0 ]]; then
for pattern in "${patterns[#]}"; do
[[ i -lt ${#common_messages[#]} ]] || break
if [[ i -lt 0 ]]; then
value="$common_status"
else
value="${common_messages[i]}"
fi
case $compare in
[ne]) [[ ! $value == "$pattern" ]] || break 2;;
[op]) [[ ! $value == $pattern ]] || break 2;;
[tr]) [[ ! $value =~ $pattern ]] || break 2;;
esac
done
fi
if [[ $compare == [not] ]]; then
let "++i,1"
continue 2
else
status="1"
break 2
fi
done
if [[ $compare == [not] ]]; then
status="1"
break
else
let "++i,1"
fi
done
[[ $options == *f* ]] || set +f
return "$status"
}
common.hctaC() {
common.TryCatchFinallyVerify || return
common.TryCatchFinallyNext "[c]" "h" || return
[[ $# -ne 1 || $1 != -r ]] || common_status="0"
}
common.Finally() {
common.TryCatchFinallyVerify || return
common.TryCatchFinallyNext "[ych]" "f" || return
}
common.yllaniF() {
common.TryCatchFinallyVerify || return
common.TryCatchFinallyNext "[f]" "l" || return
[[ common_status -eq 0 ]] || common.Throw
}
common.Caught() {
common.TryCatchFinallyVerify || return
[[ common_status -eq 0 ]] || return 1
}
common.EchoExitStatus() {
return "${1:-$?}"
}
common.EnableThrowOnError() {
common.TryCatchFinallyVerify || return
[[ $common_options == *e* ]] || common_options+="e"
}
common.DisableThrowOnError() {
common.TryCatchFinallyVerify || return
common_options="${common_options/e}"
}
common.GetStatus() {
common.TryCatchFinallyVerify || return
echo "$common_status"
}
common.SetStatus() {
common.TryCatchFinallyVerify || return
if [[ $# -ne 1 ]]; then
echo "$(common.GetAlias): $#: Wrong number of parameters" >&2
return "1"
elif [[ ${#1} -gt 16 || -n ${1%%[0-9]*} || 10#$1 -lt 1 || 10#$1 -gt 255 ]]; then
echo "$(common.GetAlias): $1: First parameter was not an integer between 1 and 255" >&2
return "1"
fi
let "common_status = 10#$1"
}
common.GetMessage() {
common.TryCatchFinallyVerify || return
local "upper=${#common_messages[#]}"
if [[ upper -eq 0 ]]; then
echo "$(common.GetAlias): $1: There are no messages" >&2
return "1"
elif [[ $# -ne 1 ]]; then
echo "$(common.GetAlias): $#: Wrong number of parameters" >&2
return "1"
elif [[ ${#1} -gt 16 || -n ${1%%[0-9]*} || 10#$1 -ge upper ]]; then
echo "$(common.GetAlias): $1: First parameter was an invalid index" >&2
return "1"
fi
echo "${common_messages[$1]}"
}
common.MessageCount() {
common.TryCatchFinallyVerify || return
echo "${#common_messages[#]}"
}
common.CopyMessages() {
common.TryCatchFinallyVerify || return
if [[ $# -ne 1 ]]; then
echo "$(common.GetAlias): $#: Wrong number of parameters" >&2
return "1"
elif [[ ${#common_messages} -gt 0 ]]; then
eval "$1=(\"\${common_messages[#]}\")"
else
eval "$1=()"
fi
}
common.TryCatchFinallyExists() {
[[ ${common_fifo:-u} != u ]]
}
common.TryCatchFinallyVerify() {
local "name"
if ! common.TryCatchFinallyExists; then
echo "$(common.GetAlias "1"): No Try-Catch-Finally exists" >&2
return "2"
fi
}
common.GetOptions() {
local "opt"
local "name=$(common.GetAlias "1")"
if common.TryCatchFinallyExists; then
echo "$name: A Try-Catch-Finally already exists" >&2
return "1"
fi
let "OPTIND = 1"
let "OPTERR = 0"
while getopts ":cdeh:ko:u:v:" opt "$#"; do
case $opt in
c) [[ $common_options == *c* ]] || common_options+="c";;
d) [[ $common_options == *d* ]] || common_options+="d";;
e) [[ $common_options == *e* ]] || common_options+="e";;
h) common_errHandler="$OPTARG";;
k) [[ $common_options == *k* ]] || common_options+="k";;
o) common_file="$OPTARG";;
u) common_unhandled="$OPTARG";;
v) common_command="$OPTARG";;
\?) #echo "Invalid option: -$OPTARG" >&2
echo "$name: Illegal option: $OPTARG" >&2
return "1";;
:) echo "$name: Option requires an argument: $OPTARG" >&2
return "1";;
*) echo "$name: An error occurred while parsing options." >&2
return "1";;
esac
done
shift "$((OPTIND - 1))"
if [[ $# -lt 1 ]]; then
echo "$name: The fifo_file parameter is missing" >&2
return "1"
fi
common_fifo="$1"
if [[ ! -p $common_fifo ]]; then
echo "$name: $1: The fifo_file is not an open FIFO" >&2
return "1"
fi
shift
if [[ $# -lt 1 ]]; then
echo "$name: The function parameter is missing" >&2
return "1"
fi
common_function="$1"
if ! chmod "0600" "$common_fifo"; then
echo "$name: $common_fifo: Can not change file mode to 0600" >&2
return "1"
fi
local "message=" "eof=TRY_CATCH_FINALLY_END_OF_FILE_$RANDOM"
{ echo "$eof" >"$common_fifo"; } 2>"/dev/null"
if [[ $? -ne 0 ]]; then
echo "$name: $common_fifo: Can not write" >&2
return "1"
fi
{ while [[ $message != *$eof ]]; do
read "message"
done <"$common_fifo"; } 2>"/dev/null"
if [[ $? -ne 0 ]]; then
echo "$name: $common_fifo: Can not read" >&2
return "1"
fi
return "0"
}
common.DefaultUnhandled() {
local -i "i"
echo "-------------------------------------------------"
echo "$(common.GetAlias "common.TryCatchFinally"): Unhandeled exception occurred"
echo "Status: $(GetStatus)"
echo "Messages:"
for ((i=0; i<$(MessageCount); i++)); do
echo "$(GetMessage "$i")"
done
echo "-------------------------------------------------"
}
common.TryCatchFinally() {
local "common_file=/dev/fd/2"
local "common_errHandler=common.DefaultErrHandler"
local "common_unhandled=common.DefaultUnhandled"
local "common_options="
local "common_fifo="
local "common_function="
local "common_flags=$-"
local "common_trySubshell=-1"
local "common_initSubshell=-1"
local "common_subshell"
local "common_status=0"
local "common_order=b"
local "common_command="
local "common_messages=()"
local "common_handler=$(trap -p ERR)"
[[ -n $common_handler ]] || common_handler="trap ERR"
common.GetOptions "$#" || return "$?"
shift "$((OPTIND + 1))"
[[ -z $common_command ]] || common_command+="=$"
common_command+='("$common_function" "$#")'
set -E
set +e
trap "common.ErrHandler" ERR
if true; then
common.Try
eval "$common_command"
common.EchoExitStatus
common.yrT
fi
while common.Catch; do
"$common_unhandled" >&2
break
common.hctaC -r
done
common.hctaC
[[ $common_flags == *E* ]] || set +E
[[ $common_flags != *e* ]] || set -e
[[ $common_flags != *f* || $- == *f* ]] || set -f
[[ $common_flags == *f* || $- != *f* ]] || set +f
eval "$common_handler"
return "$((common_status?2:0))"
}
Below is an example of a script which implements try/catch/finally in bash.
Like other answers to this question, exceptions must be caught after exiting a subprocess.
The example scripts start by creating an anonymous fifo, which is used to pass string messages from a command exception or throw to end of the closest try block. Here the messages are removed from the fifo and placed in an array variable. The status is returned through return and exit commands and placed in a different variable. To enter a catch block, this status must not be zero. Other requirements to enter a catch block are passed as parameters. If the end of a catch block is reached, then the status is set to zero. If the end of the finally block is reached and the status is still nonzero, then an implicit throw containing the messages and status is executed. The script requires the calling of the function trycatchfinally which contains an unhandled exception handler.
The syntax for the trycatchfinally command is given below.
trycatchfinally [-cde] [-h ERR_handler] [-k] [-o debug_file] [-u unhandled_handler] [-v variable] fifo function
The -c option adds the call stack to the exception messages.
The -d option enables debug output.
The -e option enables command exceptions.
The -h option allows the user to substitute their own command exception handler.
The -k option adds the call stack to the debug output.
The -o option replaces the default output file which is /dev/fd/2.
The -u option allows the user to substitute their own unhandled exception handler.
The -v option allows the user the option to pass back values though the use of Command Substitution.
The fifo is the fifo filename.
The function function is called by trycatchfinally as a subprocess.
Note: The cdko options were removed to simplify the script.
The syntax for the catch command is given below.
catch [[-enoprt] list ...] ...
The options are defined below. The value for the first list is the status. Subsquent values are the messages. If the there are more messages than
lists, then the remaining messages are ignored.
-e means [[ $value == "$string" ]] (the value has to match at least one string in the list)
-n means [[ $value != "$string" ]] (the value can not match any of the strings in the list)
-o means [[ $value != $pattern ]] (the value can not match any of the patterns in the list)
-p means [[ $value == $pattern ]] (the value has to match at least one pattern in the list)
-r means [[ $value =~ $regex ]] (the value has to match at least one extended regular expression in the list)
-t means [[ ! $value =~ $regex ]] (the value can not match any of the extended regular expressions in the list)
The try/catch/finally script is given below. To simplify the script for this answer, most of the error checking was removed. This reduced the size by 64%. A complete copy of this script can be found at my other answer.
shopt -s expand_aliases
alias try='{ common.Try'
alias yrt='EchoExitStatus; common.yrT; }'
alias catch='{ while common.Catch'
alias hctac='common.hctaC; done; }'
alias finally='{ common.Finally'
alias yllanif='common.yllaniF; }'
DefaultErrHandler() {
echo "Orginal Status: $common_status"
echo "Exception Type: ERR"
}
exception() {
let "common_status = 10#$1"
shift
common_messages=()
for message in "$#"; do
common_messages+=("$message")
done
}
throw() {
local "message"
if [[ $# -gt 0 ]]; then
let "common_status = 10#$1"
shift
for message in "$#"; do
echo "$message" >"$common_fifo"
done
elif [[ ${#common_messages[#]} -gt 0 ]]; then
for message in "${common_messages[#]}"; do
echo "$message" >"$common_fifo"
done
fi
chmod "0400" "$common_fifo"
exit "$common_status"
}
common.ErrHandler() {
common_status=$?
trap ERR
if [[ -w "$common_fifo" ]]; then
if [[ $common_options != *e* ]]; then
common_status="0"
return
fi
eval "${common_errHandler:-} \"${BASH_LINENO[0]}\" \"${BASH_SOURCE[1]}\" \"${FUNCNAME[1]}\" >$common_fifo <$common_fifo"
chmod "0400" "$common_fifo"
fi
if [[ common_trySubshell -eq BASH_SUBSHELL ]]; then
return
else
exit "$common_status"
fi
}
common.Try() {
common_status="0"
common_subshell="$common_trySubshell"
common_trySubshell="$BASH_SUBSHELL"
common_messages=()
}
common.yrT() {
local "status=$?"
if [[ common_status -ne 0 ]]; then
local "message=" "eof=TRY_CATCH_FINALLY_END_OF_MESSAGES_$RANDOM"
chmod "0600" "$common_fifo"
echo "$eof" >"$common_fifo"
common_messages=()
while read "message"; do
[[ $message != *$eof ]] || break
common_messages+=("$message")
done <"$common_fifo"
fi
common_trySubshell="$common_subshell"
}
common.Catch() {
[[ common_status -ne 0 ]] || return "1"
local "parameter" "pattern" "value"
local "toggle=true" "compare=p" "options=$-"
local -i "i=-1" "status=0"
set -f
for parameter in "$#"; do
if "$toggle"; then
toggle="false"
if [[ $parameter =~ ^-[notepr]$ ]]; then
compare="${parameter#-}"
continue
fi
fi
toggle="true"
while "true"; do
eval local "patterns=($parameter)"
if [[ ${#patterns[#]} -gt 0 ]]; then
for pattern in "${patterns[#]}"; do
[[ i -lt ${#common_messages[#]} ]] || break
if [[ i -lt 0 ]]; then
value="$common_status"
else
value="${common_messages[i]}"
fi
case $compare in
[ne]) [[ ! $value == "$pattern" ]] || break 2;;
[op]) [[ ! $value == $pattern ]] || break 2;;
[tr]) [[ ! $value =~ $pattern ]] || break 2;;
esac
done
fi
if [[ $compare == [not] ]]; then
let "++i,1"
continue 2
else
status="1"
break 2
fi
done
if [[ $compare == [not] ]]; then
status="1"
break
else
let "++i,1"
fi
done
[[ $options == *f* ]] || set +f
return "$status"
}
common.hctaC() {
common_status="0"
}
common.Finally() {
:
}
common.yllaniF() {
[[ common_status -eq 0 ]] || throw
}
caught() {
[[ common_status -eq 0 ]] || return 1
}
EchoExitStatus() {
return "${1:-$?}"
}
EnableThrowOnError() {
[[ $common_options == *e* ]] || common_options+="e"
}
DisableThrowOnError() {
common_options="${common_options/e}"
}
GetStatus() {
echo "$common_status"
}
SetStatus() {
let "common_status = 10#$1"
}
GetMessage() {
echo "${common_messages[$1]}"
}
MessageCount() {
echo "${#common_messages[#]}"
}
CopyMessages() {
if [[ ${#common_messages} -gt 0 ]]; then
eval "$1=(\"\${common_messages[#]}\")"
else
eval "$1=()"
fi
}
common.GetOptions() {
local "opt"
let "OPTIND = 1"
let "OPTERR = 0"
while getopts ":cdeh:ko:u:v:" opt "$#"; do
case $opt in
e) [[ $common_options == *e* ]] || common_options+="e";;
h) common_errHandler="$OPTARG";;
u) common_unhandled="$OPTARG";;
v) common_command="$OPTARG";;
esac
done
shift "$((OPTIND - 1))"
common_fifo="$1"
shift
common_function="$1"
chmod "0600" "$common_fifo"
}
DefaultUnhandled() {
local -i "i"
echo "-------------------------------------------------"
echo "TryCatchFinally: Unhandeled exception occurred"
echo "Status: $(GetStatus)"
echo "Messages:"
for ((i=0; i<$(MessageCount); i++)); do
echo "$(GetMessage "$i")"
done
echo "-------------------------------------------------"
}
TryCatchFinally() {
local "common_errHandler=DefaultErrHandler"
local "common_unhandled=DefaultUnhandled"
local "common_options="
local "common_fifo="
local "common_function="
local "common_flags=$-"
local "common_trySubshell=-1"
local "common_subshell"
local "common_status=0"
local "common_command="
local "common_messages=()"
local "common_handler=$(trap -p ERR)"
[[ -n $common_handler ]] || common_handler="trap ERR"
common.GetOptions "$#"
shift "$((OPTIND + 1))"
[[ -z $common_command ]] || common_command+="=$"
common_command+='("$common_function" "$#")'
set -E
set +e
trap "common.ErrHandler" ERR
try
eval "$common_command"
yrt
catch; do
"$common_unhandled" >&2
hctac
[[ $common_flags == *E* ]] || set +E
[[ $common_flags != *e* ]] || set -e
[[ $common_flags != *f* || $- == *f* ]] || set -f
[[ $common_flags == *f* || $- != *f* ]] || set +f
eval "$common_handler"
}
Below is an example, which assumes the above script is stored in the file named simple. The makefifo file contains the script described in this answer. The assumption is made that the file named 4444kkkkk does not exist, therefore causing an exception to occur. The error message output from the ls 4444kkkkk command is automatically suppressed until inside the appropriate catch block.
#!/bin/bash
#
if [[ $0 != ${BASH_SOURCE[0]} ]]; then
bash "${BASH_SOURCE[0]}" "$#"
return
fi
source simple
source makefifo
MyFunction3() {
echo "entered MyFunction3" >&4
echo "This is from MyFunction3"
ls 4444kkkkk
echo "leaving MyFunction3" >&4
}
MyFunction2() {
echo "entered MyFunction2" >&4
value="$(MyFunction3)"
echo "leaving MyFunction2" >&4
}
MyFunction1() {
echo "entered MyFunction1" >&4
local "flag=false"
try
(
echo "start of try" >&4
MyFunction2
echo "end of try" >&4
)
yrt
catch "[1-3]" "*" "Exception\ Type:\ ERR"; do
echo 'start of catch "[1-3]" "*" "Exception\ Type:\ ERR"'
local -i "i"
echo "-------------------------------------------------"
echo "Status: $(GetStatus)"
echo "Messages:"
for ((i=0; i<$(MessageCount); i++)); do
echo "$(GetMessage "$i")"
done
echo "-------------------------------------------------"
break
echo 'end of catch "[1-3]" "*" "Exception\ Type:\ ERR"'
hctac >&4
catch "1 3 5" "*" -n "Exception\ Type:\ ERR"; do
echo 'start of catch "1 3 5" "*" -n "Exception\ Type:\ ERR"'
echo "-------------------------------------------------"
echo "Status: $(GetStatus)"
[[ $(MessageCount) -le 1 ]] || echo "$(GetMessage "1")"
echo "-------------------------------------------------"
break
echo 'end of catch "1 3 5" "*" -n "Exception\ Type:\ ERR"'
hctac >&4
catch; do
echo 'start of catch' >&4
echo "failure"
flag="true"
echo 'end of catch' >&4
hctac
finally
echo "in finally"
yllanif >&4
"$flag" || echo "success"
echo "leaving MyFunction1" >&4
} 2>&6
ErrHandler() {
echo "EOF"
DefaultErrHandler "$#"
echo "Function: $3"
while read; do
[[ $REPLY != *EOF ]] || break
echo "$REPLY"
done
}
set -u
echo "starting" >&2
MakeFIFO "6"
TryCatchFinally -e -h ErrHandler -o /dev/fd/4 -v result /dev/fd/6 MyFunction1 4>&2
echo "result=$result"
exec >&6-
The above script was tested using GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin17). The output, from running this script, is shown below.
starting
entered MyFunction1
start of try
entered MyFunction2
entered MyFunction3
start of catch "[1-3]" "*" "Exception\ Type:\ ERR"
-------------------------------------------------
Status: 1
Messages:
Orginal Status: 1
Exception Type: ERR
Function: MyFunction3
ls: 4444kkkkk: No such file or directory
-------------------------------------------------
start of catch
end of catch
in finally
leaving MyFunction1
result=failure
Another example which uses a throw can be created by replacing function MyFunction3 with the script shown below.
MyFunction3() {
echo "entered MyFunction3" >&4
echo "This is from MyFunction3"
throw "3" "Orginal Status: 3" "Exception Type: throw"
echo "leaving MyFunction3" >&4
}
The syntax for the throw command is given below. If no parameters are present, then status and messages stored in the variables are used instead.
throw [status] [message ...]
The output, from executing the modified script, is shown below.
starting
entered MyFunction1
start of try
entered MyFunction2
entered MyFunction3
start of catch "1 3 5" "*" -n "Exception\ Type:\ ERR"
-------------------------------------------------
Status: 3
Exception Type: throw
-------------------------------------------------
start of catch
end of catch
in finally
leaving MyFunction1
result=failure