I am developing a big script which skeleton, looks like below:
#!/bin/bash
load_variables()
function_1()
function_2()
function_3()
[...]
function_n()
During each take-off, user flags are first loaded in load_variables() function.
Then script continue execution function_1() => function_2() => [...] => function_n()
I need to implement checkpoints which will be stored in log.txt.
Let's say, that script has been stoped or crashed at the function_2().
I want to save progress before each function start, store it in the log.txt and when I re-run the script again, I want to load_variables() and then jump to the crash point/checkpoint stored in log.txt.
How can I achieve that using bash?
I want to save progress before each function start, store it in the log.txt and when I re-run the script again, I want to load_variables() and then jump to the crash point/checkpoint stored in log.txt.
Do exactly that. But you can't "jump" in bash scripts - instead of "jump", just skip already run functions, that you can track. Basically, in pseudocode:
load_variables() {
if [[ -e log.txt ]]; then
. log.txt
fi
}
already_run_functions=()
checkpoint() {
# if the function was already run
if "$1" in already_run_functions[#]; then
# skip this function
return
fi
{
# save state with function name
declare -f
declare -p
} > log.txt
# run it
if ! "$#"; then
# handle errors
exit 1
fi
already_run_functions+=("$1")
}
load_variables
checkpoint function1
checkpoint function2
checkpoint function3
Overall, it's shell, it is simple. It's way better to use a build system. Simple Make is more than enough to track dependencies of multiple shell scripts and parallelize the work. Store the result in files after each task and distribute functions to multiple files.
So some real example:
rm -f log.txt
script() {
load_variables="
if [[ -e log.txt ]]; then
. log.txt
cd \"\$PWD\"
else
already_run_functions=()
fi
"
oneof() {
local i
for i in "${#:2}"; do
if [[ "$1" = "$i" ]]; then
return 0
fi
done
return 1
}
checkpoint() {
# if the function was already run
if oneof "$1" "${already_run_functions[#]}"; then
# skip this function
return
fi
{
# save state
declare -f
declare -p $(compgen -v | grep -Ev '^(BASH.*|EUID|FUNCNAME|GROUPS|PPID|SHELLOPTS|UID|SHELL|SHLVL|USER|TERM|RANDOM|PIPESTATUS|LINENO|COLUMN|LC_.*|LANG)$')
} > log.txt
# run it
if ! "$#"; then
# handle errors
echo "checkpoint: $1 failed"
exit 1
fi
already_run_functions+=("$1")
}
function1() {
echo function1
}
function2() {
echo function2
if [[ -e file ]]; then
return 1
fi
}
function3() {
echo function3
}
eval "$load_variables"
checkpoint function1
checkpoint function2
checkpoint function3
}
touch file
( script )
rm file
( script )
outputs:
function1
function2
checkpoint: function2 failed
function2
function3
This is an example with trap.
Saving function names on error with trap and $LINENO
Logfile will be removed if everything is ok
#!/bin/bash
trap 'clear_log' EXIT
trap 'log_checkpoint $LINENO' ERR
CHECKLOG=checkpoints.log
clear_log() {
if [ $? -eq 0 ] ; then
if [ -f "$CHECKLOG" ]; then
rm "$CHECKLOG"
fi
fi
}
log_checkpoint() {
func=$(sed -n $1p $0)
echo "Error on line $1: $func"
echo "$func" > $CHECKLOG
exit 1
}
retry(){
[ ! -f $CHECKLOG ] && return 0
if grep -q "$1" "$CHECKLOG"; then
echo retry "$1"; rm "$CHECKLOG"; return 0
else
echo skip "$1"; return 1
fi
}
func1(){
retry ${FUNCNAME[0]} || return 0
echo hello | grep hello
}
func2(){
retry ${FUNCNAME[0]} || return 0
echo hello |grep hello
}
func3(){
retry ${FUNCNAME[0]} || return 0
echo hello | grep foo
}
func1
func2
func3
exit 0
Here is my proposal, based on the above answers.
It can be helpful for people who need to trap CTRL + C and other crashes except for errors:
#!/bin/bash
### Catch crash in trap and save the function name in anchor.log
trap 'echo $anchor > anchor.log && exit 1' SIGINT
trap 'echo $anchor > anchor.log && exit 1' SIGHUP
trap 'echo $anchor > anchor.log && exit 1' SIGKILL
trap 'echo $anchor > anchor.log && exit 1' SIGTERM
### ---
clear_log() {
### REMOVING LOG IF PROGRAM EXIT NORMALLY
if [ -f "anchor.log" ]; then
rm "anchor.log"
fi
}
anchor_check(){
### RETRY FUNCTION IF IT'S NOT IN anchor.log
anchor=$1
# Check if function name is inside "anchor.log"
[ ! -f "anchor.log" ] && return 0
if grep -q "$1" "anchor.log"; then
rm "anchor.log"; return 0
else
return 1
fi
}
### EACH FUNCTION START WITH anchor_check
function_1() {
anchor_check "${FUNCNAME[0]}" || return 0
echo "test $anchor"
sleep 2
}
function_2() {
anchor_check "${FUNCNAME[0]}" || return 0
echo "test $anchor"
sleep 2
}
function_3() {
anchor_check "${FUNCNAME[0]}" || return 0
echo "test $anchor"
}
function_1
function_2
function_3
clear_log
Thank you guys for your help!
I want compare the number of files on the remote server and my local directory. I ssh into the server and I was able to capture the output of "ls somewhere/*something | wc -l" using $expect_out(buffer) and store it as a variable. Now my problem is that how do I come back to my local computer and count the files here and compare them. After this comparison, I need to go back to the server and continue the job if the result of the comparison is acceptable.
The easiest thing to do -- including from a correctness perspective -- is to not try to have a single long-running SSH session, but multiple shorter-lived ones (potentially using SSH multiplexing to reuse a single transport between such sessions):
count_remote_files() {
local host=$1 dirname=$2 dirname_q
printf -v dirname_q '%q' "$dirname"
remote_files=$(ssh "$host" "bash -s ${dirname_q}" <<EOF
cd "$1" || exit
set -- *
if [ "$#" -eq 1 ] && [ ! -e "$1" ] && [ ! -L "$1" ]; then
echo "0"
else
echo "$#"
fi
EOF
)
}
count_local_files() {
local dirname=$1
cd "$dirname" || return
set -- *
if [ "$#" -eq 1 ] && [ ! -e "$1" ] && [ ! -L "$1" ]; then
echo "0"
else
echo "$#"
fi
}
if (( $(count_remote_files "$host" "$remote_dir") ==
$(count_local_files "$local_dir") )); then
echo "File count is identical"
else
echo "File count differs"
ssh "$host" 'echo "doing something else now"'
fi
Since you are using Expect, you can easily count the local files by using Tcl commands, since Expect is built on top of Tcl:
set num_local_files [llength [glob somewhere/*something]]
For more info see http://nikit.tcl.tk/page/Tcl+Tutorial+Lesson+25
I have a condition which seems to always be evaluated as true.
#!/bin/bash
checkFolder() {
echo "[checkFolder]"
echo "check $1"
[ -n "$1" ] && [ -d "$1" ] && return 0
echo "[/checkFolder]"
return 1
}
rootFolder=$1
echo "check $rootFolder"
checkFolder "$rootFolder"
echo "res: $res" # !! <--- I omitted this test line, as I thought it was irrelevant.
echo "ret: $?"
When I execute my script, any path will give me a return value of 0. Which means that any string I provide seems to be seen as non-empty as well as an existing directory. I tried with:
./myScript.sh "."
./myScript.sh ""
./myScript.sh "wqert"
I will aways get a return value of 0. How comes?
If I run this command in my terminal:
param=""
[ -n "$param" ] && [ -d "$param" ] && echo ok
# returns nothing
param="hello"
[ -n "$param" ] && [ -d "$param" ] && echo ok
# returns nothing
param="/home"
[ -n "$param" ] && [ -d "$param" ] && echo ok
# returns "ok"
Why doesn't it work in my script?
$? is the exit code of the last executed command. In your case, the last executed command is echo, not checkFolder.
If you want to execute other commands between running a command and checking its status, assign it to a variable with myvar=$?
What the command return changes is the "exit code" of the function.
Add this:
checkFolder "$rootFolder"
echo "the exit code was $?"
And see the effect of your return 0 and return 1.
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
This may turn out to be more of a thought exercise, but I am trying to echo a newline after some command I'm executing within a conditional. For example, I have:
if ssh me#host [ -e $filename ] ; then
echo "File exists remotely"
else
echo "Does not exist remotely"
fi
And want to throw in an echo after the ssh command regardless of the outcome. The reason is formatting; that way a newline will exist after the prompt for password for ssh.
First Try
if ssh me#host [ -e $filename ] && echo ; then
Because && echo would not change the conditional outcome, but bash would not execute echo if ssh returned false. Similarly,
if ssh me#host [ -e $filename ] || (echo && false) ; then
Does not work because it will short-circuit if ssh returns true.
An answer to the problem would be
ssh me#host [ -e $filename ]
result=$?
echo
if [ $result == 0 ] ; then
but was wondering if there was some similar conditional expression to do this.
Thanks.
While this would work
if foo && echo || ! echo; then
I'd prefer putting the whole thing into a function
function addecho() {
"$#" # execute command passed as arguments (including parameters)
result= $? # store return value
echo
return $result # return stored result
}
if addecho foo; then
What about this?
if ssh me#host [ -e $filename ] && echo || echo; then
I have not thought about precedence order of && and || and surely putting some parenthesis would help, but like that it works already... you get the echo both when ssh fails and when it succeeds...
Add the "echo" before the filename test
if ssh me#host "echo; [ -e $filename ]"; then
echo "File exists remotely"
else
echo "Does not exist remotely"
fi