Shell -e command - shell

I came across this shell script for OSX and I don't understand the following:
[ -e ~/Library/Application\ Support/Dock/*.db ] on line 191?
What is that command doing? I've also seen things like [ -r "$file" ]. I don't completely understand this syntax.

-e is an argument to [ command (which is an alias of test; you can read the full docs with man test). It means «if the file or directory exists». This line is harmless unless [ was redefined earlier.

Related

How to execute a test as part of bash string as executable command?

If I have a "file" that includes...
rm -rf /etc/motd
if [ -f /etc/motd]; then rm -rf /etc/motd; fi
And I try to do...
while read -r line
do
command ${line}
#$(${line})
#eval ${line}
done< "file"
The 1st line runs of course. But the 2nd command fails with if : command not found. Which I understand the error because not an explicit command. So the question is how to execute a test as part of a string as bash script logic? I tried eval, and $(), i.e. subshells, but still errors out? Tripping over the 'if' test. I need a conditional test before the command/script code is executed in a one-liner. There has to be a way to do this, right?
If your intention is to load and execute "file" from another script just do
source "file"
no need to loop over the lines.

What does -f mean in bash

I was looking at how to use runit to run gunicorn. I was looking at the bash file and I don't know what -f $PID does in
#!/bin/sh
GUNICORN=/usr/local/bin/gunicorn
ROOT=/path/to/project
PID=/var/run/gunicorn.pid
APP=main:application
if [ -f $PID ]; then rm $PID; fi
cd $ROOT
exec $GUNICORN -c $ROOT/gunicorn.conf.py --pid=$PID $APP
Google is useless in this case because searching for flags is useless
Google is useless in this case because searching for flags is useless
Fortunately, the Bash Reference Manual is available online, at http://www.gnu.org/software/bash/manual/bashref.html. It's the first hit when you Google for "Bash manual". §6.4 "Bash Conditional Expressions" says:
-f file
True if file exists and is a regular file.
-f - file is a regular file (not a directory or device file)
Check this out for all file test operators:
http://tldp.org/LDP/abs/html/fto.html
The [ is the same as the command test which allows you to test certain things. Try help test to find out what the flags are. Things to be careful with are spaces - the [ needs a space after it.
-f checks if the file exists and is a regular file.
[ -f "$var" ]
Checks if $var is an existing file (regular file). Symbolic link passes this test too.

Difference between file tests in Bash

I am troubleshooting an existing Bash script and in the script it has two tests:
if [ ! -s <file_location> ] ; then
# copy the file to the file_location
if [ -s <file_location> ] ; then
# operate on the file
fi
fi
According to the Bash Tutorial, -s tests if the file is not of zero size. Would it be better to replace the ! -s test with a -e ? I could understand the second, nested test being a -s but the first one looks like it could be replaced with -e. What is the advantage here of ! -s vs -e? Am I missing something?
If the file exists but is empty, -e would pass, but the file would likely be useless. Using ! -s ensures that the file is present and contains useful content.

Bash syntax error: unexpected end of file

Forgive me for this is a very simple script in Bash. Here's the code:
#!/bin/bash
# june 2011
if [ $# -lt 3 -o $# -gt 3 ]; then
echo "Error... Usage: $0 host database username"
exit 0
fi
after running sh file.sh:
syntax error: unexpected end of file
I think file.sh is with CRLF line terminators.
run
dos2unix file.sh
then the problem will be fixed.
You can install dos2unix in ubuntu with this:
sudo apt-get install dos2unix
Another thing to check (just occured to me):
terminate bodies of single-line functions with semicolon
I.e. this innocent-looking snippet will cause the same error:
die () { test -n "$#" && echo "$#"; exit 1 }
To make the dumb parser happy:
die () { test -n "$#" && echo "$#"; exit 1; }
i also just got this error message by using the wrong syntax in an if clause
else if (syntax error: unexpected end of file)
elif (correct syntax)
i debugged it by commenting bits out until it worked
an un-closed if => fi clause will raise this as well
tip: use trap to debug, if your script is huge...
e.g.
set -x
trap read debug
I got this answer from this similar problem on StackOverflow
Open the file in Vim and try
:set fileformat=unix
Convert eh line endings to unix endings and see if that solves the
issue. If editing in Vim, enter the command :set fileformat=unix and
save the file. Several other editors have the ability to convert line
endings, such as Notepad++ or Atom
Thanks #lemongrassnginger
This was happening for me when I was trying to call a function using parens, e.g.
run() {
echo hello
}
run()
should be:
run() {
echo hello
}
run
I had the problem when I wrote "if - fi" statement in one line:
if [ -f ~/.git-completion.bash ]; then . ~/.git-completion.bash fi
Write multiline solved my problem:
if [ -f ~/.git-completion.bash ]; then
. ~/.git-completion.bash
fi
So I found this post and the answers did not help me but i was able to figure out why it gave me the error. I had a
cat > temp.txt < EOF
some content
EOF
The issue was that i copied the above code to be in a function and inadvertently tabbed the code. Need to make sure the last EOF is not tabbed.
on cygwin I needed:-
export SHELLOPTS
set -o igncr
in .bash_profile . This way I didn't need to run unix2dos
FOR WINDOWS:
In my case, I was working on Windows OS and I got the same error while running autoconf.
I simply open configure.ac file with my NOTEPAD++ IDE.
Then I converted the File with EOL conversion into Windows (CR LF) as follows:
EDIT -> EOL CONVERSION -> WINDOWS (CR LF)
Missing a closing brace on a function definition will cause this error as I just discovered.
function whoIsAnIidiot() {
echo "you are for forgetting the closing brace just below this line !"
Which of course should be like this...
function whoIsAnIidiot() {
echo "not you for sure"
}
I was able to cut and paste your code into a file and it ran correctly. If you
execute it like this it should work:
Your "file.sh":
#!/bin/bash
# june 2011
if [ $# -lt 3 -o $# -gt 3 ]; then
echo "Error... Usage: $0 host database username"
exit 0
fi
The command:
$ ./file.sh arg1 arg2 arg3
Note that "file.sh" must be executable:
$ chmod +x file.sh
You may be getting that error b/c of how you're doing input (w/ a pipe, carrot,
etc.). You could also try splitting the condition into two:
if [ $# -lt 3 ] || [ $# -gt 3 ]; then
echo "Error... Usage: $0 host database username"
exit 0
fi
Or, since you're using bash, you could use built-in syntax:
if [[ $# -lt 3 || $# -gt 3 ]]; then
echo "Error... Usage: $0 host database username"
exit 0
fi
And, finally, you could of course just check if 3 arguments were given (clean,
maintains POSIX shell compatibility):
if [ $# -ne 3 ]; then
echo "Error... Usage: $0 host database username"
exit 0
fi
In my case, there is a redundant \ in the like following:
function foo() {
python tools/run_net.py \
--cfg configs/Kinetics/X3D_8x8_R50.yaml \
NUM_GPUS 1 \
TRAIN.BATCH_SIZE 8 \
SOLVER.BASE_LR 0.0125 \
DATA.PATH_TO_DATA_DIR ./afs/kinetics400 \
DATA.PATH_PREFIX ./afs/kinetics400 \ # Error
}
There is NOT a \ at the end of DATA.PATH_PREFIX ./afs/kinetics400
I just cut-and-pasted your example into a file; it ran fine under bash. I don't see any problems with it.
For good measure you may want to ensure it ends with a newline, though bash shouldn't care. (It runs for me both with and without the final newline.)
You'll sometimes see strange errors if you've accidentally embedded a control character in the file. Since it's a short script, try creating a new script by pasting it from your question here on StackOverflow, or by simply re-typing it.
What version of bash are you using? (bash --version)
Good luck!
Make sure the name of the directory in which the .sh file is present does not have a space character. e.g: Say if it is in a folder called 'New Folder', you're bound to come across the error that you've cited. Instead just name it as 'New_Folder'. I hope this helps.
Apparently, some versions of the shell can also emit this message when the final line of your script lacks a newline.
In Ubuntu:
$ gedit ~/.profile
Then, File -> Save as and set end line to Unix/Linux
I know I am too late to the party. Hope this may help someone.
Check your .bashrc file. Perhaps rename or move it.
Discussion here: Unable to source a simple bash script
For people using MacOS:
If you received a file with Windows format and wanted to run on MacOS and seeing this error, run these commands.
brew install dos2unix
sh <file.sh>
If the the script itself is valid and there are no syntax errors, then some possible causes could be:
Invalid end-of-lines (for example, \r\n instead of \n)
Presence of the byte order mark (BOM) at the beginning of the file
Both can be fixed using vim or vi.
To fix line endings open the file in vim and from the command mode type:
:set ff=unix
To remove the BOM use:
:set nobomb
For those who don't have dos2unix installed (and don't want to install it):
Remove trailing \r character that causes this error:
sed -i 's/\r$//' filename
Details from this StackOverflow answer. This was really helpful.
https://stackoverflow.com/a/32912867/7286223

Sourcing a script file in bash before starting an executable

I'm trying to write a bash script that "wraps" whatever the user wants to invoke (and its parameters) sourcing a fixed file just before actually invoking it.
To clarify: I have a "ConfigureMyEnvironment.bash" script that must be sourced before starting certain executables, so I'd like to have a "LaunchInMyEnvironment.bash" script that you can use as in:
LaunchInMyEnvironment <whatever_executable_i_want_to_wrap> arg0 arg1 arg2
I tried the following LaunchInMyEnvironment.bash:
#!/usr/bin/bash
launchee="$#"
if [ -e ConfigureMyEnvironment.bash ];
then source ConfigureMyEnvironment.bash;
fi
exec "$launchee"
where I have to use the "launchee" variable to save the $# var because after executing source, $# becomes empty.
Anyway, this doesn't work and fails as follows:
myhost $ LaunchInMyEnvironment my_executable -h
myhost $ /home/me/LaunchInMyEnvironment.bash: line 7: /home/bin/my_executable -h: No such file or directory
myhost $ /home/me/LaunchInMyEnvironment.bash: line 7: exec: /home/bin/my_executable -h: cannot execute: No such file or directory
That is, it seems like the "-h" parameter is being seen as part of the executable filename and not as a parameter... But it doesn't really make sense to me.
I tried also to use $* instead of $#, but with no better outcoume.
What I'm doing wrong?
Andrea.
Have you tried to remove double quotes in exec command?
Try this:
#!/usr/bin/bash
typeset -a launchee
launchee=("$#")
if [ -e ConfigureMyEnvironment.bash ];
then source ConfigureMyEnvironment.bash;
fi
exec "${launchee[#]}"
That will use arrays for storing arguments, so it will handle even calls like "space delimited string" and "string with ; inside"
Upd: simple example
test_array() { abc=("$#"); for x in "${abc[#]}"; do echo ">>$x<<"; done; }
test_array "abc def" ghi
should give
>>abc def<<
>>ghi<<
You might want to try this (untested):
#!/usr/bin/bash
launchee="$1"
shift
if [ -e ConfigureMyEnvironment.bash ];
then source ConfigureMyEnvironment.bash;
fi
exec "$launchee" $#
The syntax for exec is exec command [arguments], however becuase you've quoted $launchee, this is treated as a single argument - i.e., the command, rather than a command and it's arguments. Another variation may be to simply do: exec $#
Just execute it normally without exec
#!/usr/bin/bash
launchee="$#"
if [ -e ConfigureMyEnvironment.bash ];
then source ConfigureMyEnvironment.bash;
fi
$launchee
Try dividing your list of argumets:
ALL_ARG="${#}"
Executable="${1}"
Rest_of_Args=${ALL_ARG##$Executable}
And try then:
$Executable $Rest_of_Args
(or exec $Executable $Rest_of_Args)
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