I have a shell script with the following line in it:
[ "$DEBUG" == 'true' ] && set -x
set -x enables a mode of the shell where all executed commands are printed to the terminal. In your case it's clearly used for debugging, which is a typical use case for set -x: printing every command as it is executed may help you to visualize the control flow of the script if it is not functioning as expected.
set +x disables it.
set -x
Prints a trace of simple commands, for commands, case commands, select
commands, and arithmetic for commands and their arguments or
associated word lists after they are expanded and before they are
executed. The value of the PS4 variable is expanded and the resultant
value is printed before the command and its expanded arguments.
[source]
Example
set -x
echo `expr 10 + 20 `
+ expr 10 + 20
+ echo 30
30
set +x
echo `expr 10 + 20 `
30
Above example illustrates the usage of set -x. When it is used, above arithmetic expression has been expanded. We could see how a single line has been evaluated step by step.
First step expr has been evaluated.
Second step echo has been evaluated.
To know more about set → visit this link
when it comes to your shell script,
[ "$DEBUG" == 'true' ] && set -x
Your script might have been printing some additional lines of information when the execution mode selected as DEBUG. Traditionally people used to enable debug mode when a script called with optional argument such as -d
-u: disabled by default. When activated, an error message is displayed when using an unconfigured variable.
-v: inactive by default. After activation, the original content of the information will be displayed (without variable resolution) before the
information is output.
-x: inactive by default. If activated, the command content will be displayed before the command is run (after variable resolution, there
is a ++ symbol).
Compare the following differences:
/ # set -v && echo $HOME
/root
/ # set +v && echo $HOME
set +v && echo $HOME
/root
/ # set -x && echo $HOME
+ echo /root
/root
/ # set +x && echo $HOME
+ set +x
/root
/ # set -u && echo $NOSET
/bin/sh: NOSET: parameter not set
/ # set +u && echo $NOSET
Related
I am trying to make a simple thing to make my teammates lives easier. They are constantly copying quote into the command line that are formatted which breaks the command ie: “test“ vs. "test"
It's proved surprisingly annoying to do with:
function damn() { !!:gs/“/" }
or:
alias damn='!!:gs/“/"'
Neither seems to work and keeps giving me either the error
-bash: !!:gs/“/" : No such file or directory
or just:
>
I must be missing something obvious here.
! does not work in functions or aliases. According to bash manual:
History expansion is performed immediately after a complete line is read, before the shell breaks it into words.
You can use the builtin fc command:
[STEP 100] # echo $BASH_VERSION
4.4.19(1)-release
[STEP 101] # alias damn='fc -s “=\" ”=\" '
[STEP 102] # echo “test”
“test”
[STEP 103] # damn
echo "test"
test
[STEP 104] #
For quick referecne, the following is output of help fc.
fc: fc [-e ename] [-lnr] [first] [last] or fc -s [OLD=NEW] [command]
Display or execute commands from the history list.
fc is used to list or edit and re-execute commands from the history list.
FIRST and LAST can be numbers specifying the range, or FIRST can be a
string, which means the most recent command beginning with that
string.
Options:
-e ENAME select which editor to use. Default is FCEDIT, then EDITOR,
then vi
-l list lines instead of editing
-n omit line numbers when listing
-r reverse the order of the lines (newest listed first)
| With the `fc -s [OLD=NEW ...] [command]' format, COMMAND is
| re-executed after the substitution OLD=NEW is performed.
A useful alias to use with this is r='fc -s', so that typing `r cc'
runs the last command beginning with `cc' and typing `r' re-executes
the last command.
Exit Status:
Returns success or status of executed command; non-zero if an error occurs.
Here is a slightly more general solution using a bash function to wrap the fc call, if you want to do something to the string beyond substitution.
function damn() {
# Capture the previous command.
cmd=$(fc -ln -1)
# Do whatever you want with cmd here
cmd=$(echo $cmd | sed 's/[“”]/"/g')
# Re-run the command
eval $cmd
}
I am using the following code in a bash script in order to trace the code
#!/bin/bash
function trace()
{
echo "TRACE" \
"${BASH_SOURCE[1]}:${BASH_LINENO[0]}:${FUNCNAME[1]}:" \
"$BASH_COMMAND"
}
set -o functrace
shopt -s extdebug
trap trace DEBUG
# Remainder of code here
exit 0
But when I run it, it eats my variables.
Some clue?
The best way is to use set -xv. The set -v will echo a line before it is executed. The set -x will output the line after the shell script interpolates the variables and expressions in that line.
As part of this, you can also create an environment variable called PS4 which will be the prompt printed each time your shell scripts outputs the line being executed. Most people set it to something like PS="\$LINENO: " which will print out the line number for the line being executed.
Once you're finished, you can turn off debugging by setting set +xv.
#
# Somewhere in this part of my script, I am having problems....
#
export PS4="\$LINENO> " # Now, I'll see the line numbers while debugging
set -xv # Debugging is turned on
....
#
# Done with debugging
#
set +xv # Debugging is turned off
Here are a few recommendations:
You can always echo line in your shell script to see what's going on.
You can also use set -xv to help you debug a shell script. Simply put set -xv before the part you want to debug, and set +xv to turn off the debug. You can also use export PS4="\$LINENO> " to print out the line number in your shell script.
Here's how your script will look with the set -xv. It's a really nice tool for debugging shell scripts.
The following setup will enable printing of the line number and function name for each command (assuming you later put set -x in front of the code you're debugging):
set -o functrace
shopt -s extdebug
PS4='+ line ${LINENO-}, in ${FUNCNAME-}(): '
Here's some code to test the above:
foo() { echo "now in $FUNCNAME"; bar; }
bar() { echo "now in $FUNCNAME"; baz; }
baz() { echo "now in $FUNCNAME"; }
set -x
foo
I've been using "set -x" inside bash scripts in order to help me debug some functions, and it has been working very well for me
-x After expanding each simple command, for command, case command,
select command, or arithmetic for command, display the expanded
value of PS4, followed by the command and its expanded arguments or
associated word list.
However I'd like to be able to clear it before I leave the function
Eg:
#/bin bash
function somefunction()
{
set -x
# some code I'm debugging
# clear the set -x
set ????
}
somefunction
Quoting the manual:
Using + rather than - causes these flags to be turned off.
So it's set +x what you are looking for.
Consider a function like
foo () {
set -x
# do something
set +x
}
The problem is that if the -x option was already set before foo was called, it will be turned off by foo.
If you want to restore the old value, you'll have to test whether it was enabled already using $-.
foo () {
[[ $- != *x* ]]; x_set=$? # 1 if already set, 0 otherwise
set -x
# do something
(( x_set )) || set +x # Turn off -x if it was off before
}
For some more info always refer to the basic guide. This clearly gives you the answer :
http://www.tldp.org/LDP/Bash-Beginners-Guide/html/Bash-Beginners-Guide.html
set -x # activate debugging from here
w
set +x # stop debugging from here
There are many questions asking about accessing the Sublime Text 2 editor from the command line. The responses, in summary, are to make a symlink, alias or simple shell script to run the appropriate sublime_text command. I can do that. What I want is to make the linux version behave like the MacOS version.
On MacOS, I have the following:
ln -s /Applications/Sublime\ Text\ 2.app/Contents/SharedSupport/bin/subl ~/bin/subl
Then in my .zshrc:
alias subl="$HOME/bin/subl -n"
export EDITOR="$HOME/bin/subl -n -w"
This does two things. It gives me a subl command that opens any files given on the command line in a new window. The subl command does not block the terminal. It also sets up my editor to open sublime text to edit the arguments, but this time it does block. In particular, $EDITOR blocks until its arguments are closed. It does not block on unrelated sublime text windows.
I can achieve a similar effect on linux with the following:
In ~/bin/subl:
#! /bin/zsh
$HOME/Sublime\ Text\ 2/sublime_text -n $# &
and then in ~/bin/subl_wait: (think mate_wait for TextMate users)
#! /bin/zsh
exec $HOME/Sublime\ Text\ 2/sublime_text -n -w $#
I can then set EDITOR to subl_wait, and things almost work. subl opens files for editing and doesn't block. subl_wait opens files for editing and does block.
The problem is that subl_wait is waiting until all open files are closed, not just its arguments.
Is it possible to get this working perfectly?
Looks like I've found the issue. (Thanks to this post: http://www.sublimetext.com/forum/viewtopic.php?f=2&t=7003 )
Basic point: sublime behaves differently depending upon whether an instance is already running!
If an instance is already running then sublime on linux behaves similarly to MacOS. If no instance is running then the terminal blocks until you exit sublime.
With that in mind, we just need to modify the scripts to make sure sublime is running:
in ~/bin/subl_start:
#! /bin/zsh
if [ ! "$(pidof sublime_text)" ] ; then
# start sublime text main instance
# echo "Starting Sublime Text 2"
$HOME/Sublime\ Text\ 2/sublime_text &
sleep 1 # needed to avoid a race condition
fi
in ~/bin/subl:
#! /bin/zsh
. $HOME/bin/subl_start
exec $HOME/Sublime\ Text\ 2/sublime_text -n $#
in ~/bin/subl_wait:
#! /bin/zsh
. $HOME/bin/subl_start
exec $HOME/Sublime\ Text\ 2/sublime_text -n -w $#
Note that I've used the -n flags everywhere. This might not be your cup of tea. If you are using -n then you possibly also want to look at your close_windows_when_empty setting.
Inspired by the OP's answer, I've created a bash wrapper script for Sublime Text that incorporates all your findings and runs on both OSX and Linux.
Its purpose is threefold:
provide a unified subl CLI that works like ST's own subl on OSX: invoke ST without blocking, unless waiting is explicitly requested.
encapsulate a workaround for the waiting-related bug on Linux.
when saved or symlinked to as sublwait, provide a sublwait CLI that automatically applies the --wait and --new-window options so as to make it suitable for use with $EDITOR (note that some programs, e.g. npm, require the $EDITOR to contain the name of an executable only - executables + options are not supported); also makes sure that at least one file is specified.
The only open question is whether the OP's approach to avoiding the race condition - sleep 1 - is robust enough.
Update:
Note that subl on OSX is by default NOT placed in the $PATH - you normally have to do that manually. If you haven't done so, the script will now locate subl inside ST's application bundle; (it tries app names in the following sequence: 'Sublime Text', 'Sublime Text 2', 'Sublime Text 3', first in /Applications, then in ~/Applications.)
Here's the output from running the script with -h:
Multi-platform (OSX, Linux) wrapper script for invocation of Sublime Text (ST)
from the command line.
Linux:
Works around undesired blocking of the shell (unless requested)
and a bug when waiting for specific files to be edited.
Both platforms:
When invoked as `sublwait`, automatically applies the
--wait --new-window
options to make it suitable for use with $EDITOR.
Therefore, you can to the following:
- Name this script `subl` for a CLI that supports ALL options.
(On OSX, this will simply defer to the `subl` CLI that came with ST.)
- Place the script in a directory in your $PATH.
- In the same directory, create a symlink to the `subl` script named
`sublwait`:
ln -s subl sublwait
and, if desired, add
export EDITOR=sublwait
to your shell profile.
Note that if you only use OSX, you can make do with ST's own subl and just save this script directly as sublwait.
Script source:
#!/usr/bin/env bash
# Multi-platform (OSX, Linux) wrapper script for invocation of Sublime Text (ST)
# from the command line. Invoke with -h for details.
[[ $1 == '-h' || $1 == '--help' ]] && showHelpOnly=1 || showHelpOnly=0
[[ $(basename "$BASH_SOURCE") == 'sublwait' ]] && invokedAsSublWait=1 || invokedAsSublWait=0
[[ $(uname) == 'Darwin' ]] && isOsX=1 || isOsX=0
# Find the platform-appropriate ST executable.
if (( isOsX )); then # OSX: ST comes with a bona-fide CLI, `subl`.
# First, try to find the `subl` CLI in the $PATH.
# Note: This CLI is NOT there by default; it must be created by symlinking it from
# its location inside the ST app bundle.
# Find the `subl` executable, ignoring this script, if named subl' as well, or a
# script by that name in the same folder as this one (when invoked via symlink 'sublwait').
stExe=$(which -a subl | fgrep -v -x "$(dirname "$BASH_SOURCE")/subl" | head -1)
# If not already in the path, look for it inside the application bundle. Try several locations and versions.
if [[ -z $stExe ]]; then
for p in {,$HOME}"/Applications/Sublime Text"{,' 2',' 3'}".app/Contents/SharedSupport/bin/subl"; do
[[ -f $p ]] && { stExe=$p; break; }
done
fi
[[ -x $stExe ]] || { echo "ERROR: Sublime Text CLI 'subl' not found." 1>&2; exit 1; }
else # Linux: `sublime_text` is the only executable - the app itself.
stExe='sublime_text'
which "$stExe" >/dev/null || { echo "ERROR: Sublime Text executable '$stExe' not found." 1>&2; exit 1; }
fi
# Show command-line help, if requested.
# Add preamble before printing ST's own help.
# Note that we needn't worry about blocking the
# shell in this case - ST just outputs synchronously
# to stdout, then exits.
if (( showHelpOnly )); then
bugDescr=$(
cat <<EOF
works around a bug on Linux (as of v2.0.2), where Sublime Text,
if it is not already running, mistakenly blocks until it is exited altogether.
EOF
)
if (( invokedAsSublWait )); then
# We provide variant-specific help here.
cat <<EOF
Wrapper script for Sublime Text suitable for use with the \$EDITOR variable.
Opens the specified files for editing in a new window and blocks the
invoking program (shell) until they are closed.
In other words: the --wait and --new-window options are automatically
applied.
Aside from encapsulating this functionality without the need for options
- helpful for tools that require \$EDITOR to be an executable name only -
$bugDescr
Usage: sublwait file ...
EOF
# Note: Adding other options doesn't make sense in this scenario
# (as of v2.0.2), so we do NOT show ST's own help here.
else
cat <<EOF
Multi-platform (OSX, Linux) wrapper script for invocation of
Sublime Text (ST) from the command line.
Linux:
Works around undesired blocking of the shell (unless requested)
and a bug when waiting for specific files to be edited.
Both platforms:
When invoked as \`sublwait\`, automatically applies the
--wait --new-window
options to make it suitable for use with \$EDITOR.
Therefore, you can to the following:
- Name this script \`subl\` for a CLI that supports ALL options.
(On OSX, this will simply defer to the \`subl\` CLI that came with ST.)
- Place the script in a directory in your \$PATH.
- In the same directory, create a symlink to the \`subl\` script named
\`sublwait\`:
ln -s subl sublwait
and, if desired, add
export EDITOR=sublwait
to your shell profile.
Sublime Text's own help:
------------------------
EOF
# Finally, print ST's own help and exit.
exec "$stExe" "$#"
fi
exit 0
fi
# Invoked as `sublwait`? -> automatically apply --wait --new-window options.
if (( invokedAsSublWait )); then
# Validate parameters.
# - We expect NO options - to keep things simple and predictable, we do NOT allow
# specifying additional options (beyond the implied ones).
# - We need at least 1 file argument.
# - As a courtesy, we ensure that no *directories* are among the arguments - ST doesn't support
# that properly (always waits for ST exit altogether); beyond that, however, we leave input
# validation to ST.
if [[ "$1" =~ ^-[[:alnum:]]+$ || "$1" =~ ^--[[:alnum:]]+[[:alnum:]-]+$ ]]; then # options specified?
{ echo "ERROR: Unexpected option specified: '$1'. Use -h for help." 1>&2; exit 1; }
elif (( $# == 0 )); then # no file arguments?
{ echo "ERROR: Missing file argument. Use -h for help." 1>&2; exit 1; }
else # any directories among the arguments?
# Note: We do NOT check for file existence - files could be created on demand.
# (Things can still go wrong - e.g., /nosuchdir/mynewfile - and ST doesn't
# handle that gracefully, but we don't want to do too much here.)
for f in "$#"; do
[[ ! -d "$f" ]] || { echo "ERROR: Specifying directories is not supported: '$f'. Use -h for help." 1>&2; exit 1; }
done
fi
# Prepend the implied options.
set -- '--wait' '--new-window' "$#"
fi
# Finally, invoke ST:
if (( isOsX )); then # OSX
# `subl` on OSX handles all cases correctly; simply pass parameters through.
exec "$stExe" "$#"
else # LINUX: `sublime_text`, the app executable itself, does have a CLI, but it blocks the shell.
# Determine if the wait option was specified.
mustWait=0
if (( invokedAsSublWait )); then
mustWait=1
else
# Look for the wait option in the parameters to pass through.
for p in "$#"; do
[[ $p != -* ]] && break # past options
[[ $p == '--wait' || $p =~ ^-[[:alnum:]]*w[[:alnum:]]*$ ]] && { mustWait=1; break; }
done
fi
if (( mustWait )); then # Invoke in wait-for-specified-files-to-close mode.
# Quirk on Linux:
# If sublime_text isn't running yet, we must start it explicitly first.
# Otherwise, --wait will wait for ST *as a whole* to be closed before returning,
# which is undesired.
# Thanks, http://stackoverflow.com/questions/14598261/making-sublime-text-2-command-on-linux-behave-as-it-does-on-macos-x
if ! pidof "$stExe" 1>/dev/null; then
# Launch as BACKGROUND task to avoid blocking.
# (Sadly, the `--background` option - designed not to activate the Sublime Text window
# on launching - doesn't actually work on Linux (as of ST v2.0.2 on Ubuntu 12.04).)
("$stExe" --background &)
# !! We MUST give ST some time to start up, otherwise the 2nd invocation below will be ignored.
# ?? Does a fixed sleep time of 1 second work reliably?
sleep 1
fi
# Invoke in blocking manner, as requested.
exec "$stExe" "$#"
else # Ensure invocation in NON-blocking manner.
if ! pidof "$stExe" 1>/dev/null; then # ST isn't running.
# If ST isn't running, invoking it *always* blocks.
# Therefore, we launch it as a background taks.
# Invocation via a subshell (parentheses) suppresses display of the
# background-task 'housekeeping' info.
("$stExe" "$#" &)
else # ST is already running, we can safely invoke it directly without fear of blocking.
exec "$stExe" "$#"
fi
fi
fi
On Ubuntu Gnu/Linux 13.04 64-bit:
I just keep subl running pretty much all the time. So my git config has:
core.editor=/usr/bin/subl -n -w
And that's all I need. I save the git commit file with ctrl-s, close the window with ctrl-w and I'm done. But I then have to really close the window by hitting the X in the upper corner... 96% perfect.
I am trying to do a homework assignment and it is very confusing. I am not sure if the professor's example is in Perl or bash, since it has no header. Basically, I just need help with the meat of the problem: capturing the input and outputting it. Here is the assignment:
In the session, provide a command prompt that includes the working directory, e.g.,
$./logger/home/it244/it244/hw8$
Accept user’s commands, execute them, and display the output on the screen.
During the session, create a temporary file “PID.cmd” (PID is the process ID) to store the command history in the following format (index: command):
1: ls
2: ls -l
If the script is aborted by CTRL+C (signal 2), output a message “aborted by ctrl+c”.
When you quit the logging session (either by “exit” or CTRL+C),
a. Delete the temporary file
b. Print out the total number of the commands in the session and the numbers of successful/failed commands (according to the exit status).
Here is my code so far (which did not go well, I would not try to run it):
#!/bin/sh
trap 'exit 1' 2
trap 'ctrl-c' 2
echo $(pwd)
while true
do
read -p command
echo "$command:" $command >> PID.cmd
done
Currently when I run this script I get
command read: 10: arg count
What is causing that?
======UPDATE=========
Ok I made some progress not quite working all the way it doesnt like my bashtrap or incremental index
#!/bin/sh
index=0
trap bashtrap INT
bashtrap(){
echo "CTRL+C aborting bash script"
}
echo "starting to log"
while :
do
read -p "command:" inputline
if [ $inputline="exit" ]
then
echo "Aborting with Exit"
break
else
echo "$index: $inputline" > output
$inputline 2>&1 | tee output
(( index++ ))
fi
done
This can be achieved in bash or perl or others.
Some hints to get you started in bash :
question 1 : command prompt /logger/home/it244/it244/hw8
1) make sure of the prompt format in the user .bashrc setup file: see PS1 data for debian-like distros.
2) cd into that directory within you bash script.
question 2 : run the user command
1) get the user input
read -p "command : " input_cmd
2) run the user command to STDOUT
bash -c "$input_cmd"
3) Track the user input command exit code
echo $?
Should exit with "0" if everything worked fine (you can also find exit codes in the command man pages).
3) Track the command PID if the exit code is Ok
echo $$ >> /tmp/pid_Ok
But take care the question is to keep the user command input, not the PID itself as shown here.
4) trap on exit
see man trap as you misunderstood the use of this : you may create a function called on the catched exit or CTRL/C signals.
5) increment the index in your while loop (on the exit code condition)
index=0
while ...
do
...
((index++))
done
I guess you have enough to start your home work.
Since the example posted used sh, I'll use that in my reply. You need to break down each requirement into its specific lines of supporting code. For example, in order to "provide a command prompt that includes the working directory" you need to actually print the current working directory as the prompt string for the read command, not by setting the $PS variable. This leads to a read command that looks like:
read -p "`pwd -P`\$ " _command
(I use leading underscores for private variables - just a matter of style.)
Similarly, the requirement to do several things on either a trap or a normal exit suggests a function should be created which could then either be called by the trap or to exit the loop based on user input. If you wanted to pretty-print the exit message, you might also wrap it in echo commands and it might look like this:
_cleanup() {
rm -f $_LOG
echo
echo $0 ended with $_success successful commands and $_fail unsuccessful commands.
echo
exit 0
}
So after analyzing each of the requirements, you'd need a few counters and a little bit of glue code such as a while loop to wrap them in. The result might look like this:
#/usr/bin/sh
# Define a function to call on exit
_cleanup() {
# Remove the log file as per specification #5a
rm -f $_LOG
# Display success/fail counts as per specification #5b
echo
echo $0 ended with $_success successful commands and $_fail unsuccessful commands.
echo
exit 0
}
# Where are we? Get absolute path of $0
_abs_path=$( cd -P -- "$(dirname -- "$(command -v -- "$0")")" && pwd -P )
# Set the log file name based on the path & PID
# Keep this constant so the log file doesn't wander
# around with the user if they enter a cd command
_LOG=${_abs_path}/$$.cmd
# Print ctrl+c msg per specification #4
# Then run the cleanup function
trap "echo aborted by ctrl+c;_cleanup" 2
# Initialize counters
_line=0
_fail=0
_success=0
while true
do
# Count lines to support required logging format per specification #3
((_line++))
# Set prompt per specification #1 and read command
read -p "`pwd -P`\$ " _command
# Echo command to log file as per specification #3
echo "$_line: $_command" >>$_LOG
# Arrange to exit on user input with value 'exit' as per specification #5
if [[ "$_command" == "exit" ]]
then
_cleanup
fi
# Execute whatever command was entered as per specification #2
eval $_command
# Capture the success/fail counts to support specification #5b
_status=$?
if [ $_status -eq 0 ]
then
((_success++))
else
((_fail++))
fi
done