i run the following function in (git-)bash under windows:
function config_get_container_values() {
local project_name=$1
local container_name=$2
#local container_name="gitea"
echo "###"
buildcmd="jq -r \".containers[]."
echo "$buildcmd"
buildcmd="${buildcmd}${container_name}"
echo "$buildcmd"
buildcmd="${buildcmd}foobar"
echo "$buildcmd"
echo "###"
}
The output of this is the following. Whyever, after using the variable to extend the string, he starts to overwrite $buildcmd. I tried this also with everything in one line as well with the append command (=+). Everytime the same result.
###
jq -r ".containers[].
jq -r ".containers[].gitea
foobar".containers[].gitea
###
The really strange thing is: When i enable the line local container_name="gitea" everything works as expected. The output is:
###
jq -r ".containers[].
jq -r ".containers[].gitea
jq -r ".containers[].giteafoobar
###
When i put this all into a news file, its also works as expected. So i think something goes wrong in the thousands of line before calling this function. Any idea, what could be cause of this behavior?
Regards
Dave
This is not how you should build up the command, DOS line endings aside. Use --arg to pass the name into the filter as a variable. For example,
config_get_container_values() {
local project_name=$1
local container_name=$2
jq -r --arg n "$container_name " '.containers[][$n+"foobar"]'
}
config_get_container foo gitea < some.json
If the function is invoked with
config_get_container_values proj gitea
it produces the "expected" output. If it is invoked with
config_get_container_values proj $'gitea\r'
it produces output that looks like the first output example. $'gitea\r' expands to a string that consists of 'gitea' followed by a Carriage return (CR) character.
One possible cause of the problem is that the container name (gitea) was read from a file that had Windows/DOS line endings (CR-LF). Problems like that are common. See the first question ("Check whether your script or data has DOS style end-of-line characters") in the "Before asking about problematic code" section of the Stack Overflow 'bash' Info page.
Here's the problem: I have this script foo.py, and if the user invokes it without the --bar option, I'd like to display the following error message:
Please add the --bar option to your command, like so:
python foo.py --bar
Now, the tricky part is that there are several ways the user might have invoked the command:
They may have used python foo.py like in the example
They may have used /usr/bin/foo.py
They may have a shell alias frob='python foo.py', and actually ran frob
Maybe it's even a git alias flab=!/usr/bin/foo.py, and they used git flab
In every case, I'd like the message to reflect how the user invoked the command, so that the example I'm providing would make sense.
sys.argv always contains foo.py, and /proc/$$/cmdline doesn't know about aliases. It seems to me that the only possible source for this information would be bash itself, but I don't know how to ask it.
Any ideas?
UPDATE How about if we limit possible scenarios to only those listed above?
UPDATE 2: Plenty of people wrote very good explanation about why this is not possible in the general case, so I would like to limit my question to this:
Under the following assumptions:
The script was started interactively, from bash
The script was start in one of these 3 ways:
foo <args> where foo is a symbolic link /usr/bin/foo -> foo.py
git foo where alias.foo=!/usr/bin/foo in ~/.gitconfig
git baz where alias.baz=!/usr/bin/foo in ~/.gitconfig
Is there a way to distinguish between 1 and (2,3) from within the script? Is there a way to distinguish between 2 and 3 from within the script?
I know this is a long shot, so I'm accepting Charles Duffy's answer for now.
UPDATE 3: So far, the most promising angle was suggested by Charles Duffy in the comments below. If I can get my users to have
trap 'export LAST_BASH_COMMAND=$(history 1)' DEBUG
in their .bashrc, then I can use something like this in my code:
like_so = None
cmd = os.environ['LAST_BASH_COMMAND']
if cmd is not None:
cmd = cmd[8:] # Remove the history counter
if cmd.startswith("foo "):
like_so = "foo --bar " + cmd[4:]
elif cmd.startswith(r"git foo "):
like_so = "git foo --bar " + cmd[8:]
elif cmd.startswith(r"git baz "):
like_so = "git baz --bar " + cmd[8:]
if like_so is not None:
print("Please add the --bar option to your command, like so:")
print(" " + like_so)
else:
print("Please add the --bar option to your command.")
This way, I show the general message if I don't manage to get their invocation method. Of course, if I'm going to rely on changing my users' environment I might as well ensure that the various aliases export their own environment variables that I can look at, but at least this way allows me to use the same technique for any other script I might add later.
No, there is no way to see the original text (before aliases/functions/etc).
Starting a program in UNIX is done as follows at the underlying syscall level:
int execve(const char *path, char *const argv[], char *const envp[]);
Notably, there are three arguments:
The path to the executable
An argv array (the first item of which -- argv[0] or $0 -- is passed to that executable to reflect the name under which it was started)
A list of environment variables
Nowhere in here is there a string that provides the original user-entered shell command from which the new process's invocation was requested. This is particularly true since not all programs are started from a shell at all; consider the case where your program is started from another Python script with shell=False.
It's completely conventional on UNIX to assume that your program was started through whatever name is given in argv[0]; this works for symlinks.
You can even see standard UNIX tools doing this:
$ ls '*.txt' # sample command to generate an error message; note "ls:" at the front
ls: *.txt: No such file or directory
$ (exec -a foobar ls '*.txt') # again, but tell it that its name is "foobar"
foobar: *.txt: No such file or directory
$ alias somesuch=ls # this **doesn't** happen with an alias
$ somesuch '*.txt' # ...the program still sees its real name, not the alias!
ls: *.txt: No such file
If you do want to generate a UNIX command line, use pipes.quote() (Python 2) or shlex.quote() (Python 3) to do it safely.
try:
from pipes import quote # Python 2
except ImportError:
from shlex import quote # Python 3
cmd = ' '.join(quote(s) for s in open('/proc/self/cmdline', 'r').read().split('\0')[:-1])
print("We were called as: {}".format(cmd))
Again, this won't "un-expand" aliases, revert to the code that was invoked to call a function that invoked your command, etc; there is no un-ringing that bell.
That can be used to look for a git instance in your parent process tree, and discover its argument list:
def find_cmdline(pid):
return open('/proc/%d/cmdline' % (pid,), 'r').read().split('\0')[:-1]
def find_ppid(pid):
stat_data = open('/proc/%d/stat' % (pid,), 'r').read()
stat_data_sanitized = re.sub('[(]([^)]+)[)]', '_', stat_data)
return int(stat_data_sanitized.split(' ')[3])
def all_parent_cmdlines(pid):
while pid > 0:
yield find_cmdline(pid)
pid = find_ppid(pid)
def find_git_parent(pid):
for cmdline in all_parent_cmdlines(pid):
if cmdline[0] == 'git':
return ' '.join(quote(s) for s in cmdline)
return None
See the Note at the bottom regarding the originally proposed wrapper script.
A new more flexible approach is for the python script to provide a new command line option, permitting users to specify a custom string they would prefer to see in error messages.
For example, if a user prefers to call the python script 'myPyScript.py' via an alias, they can change the alias definition from this:
alias myAlias='myPyScript.py $#'
to this:
alias myAlias='myPyScript.py --caller=myAlias $#'
If they prefer to call the python script from a shell script, it can use the additional command line option like so:
#!/bin/bash
exec myPyScript.py "$#" --caller=${0##*/}
Other possible applications of this approach:
bash -c myPyScript.py --caller="bash -c myPyScript.py"
myPyScript.py --caller=myPyScript.py
For listing expanded command lines, here's a script 'pyTest.py', based on feedback by #CharlesDuffy, that lists cmdline for the running python script, as well as the parent process that spawned it.
If the new -caller argument is used, it will appear in the command line, although aliases will have been expanded, etc.
#!/usr/bin/env python
import os, re
with open ("/proc/self/stat", "r") as myfile:
data = [x.strip() for x in str.split(myfile.readlines()[0],' ')]
pid = data[0]
ppid = data[3]
def commandLine(pid):
with open ("/proc/"+pid+"/cmdline", "r") as myfile:
return [x.strip() for x in str.split(myfile.readlines()[0],'\x00')][0:-1]
pid_cmdline = commandLine(pid)
ppid_cmdline = commandLine(ppid)
print "%r" % pid_cmdline
print "%r" % ppid_cmdline
After saving this to a file named 'pytest.py', and then calling it from a bash script called 'pytest.sh' with various arguments, here's the output:
$ ./pytest.sh a b "c d" e
['python', './pytest.py']
['/bin/bash', './pytest.sh', 'a', 'b', 'c d', 'e']
NOTE: criticisms of the original wrapper script aliasTest.sh were valid. Although the existence of a pre-defined alias is part of the specification of the question, and may be presumed to exist in the user environment, the proposal defined the alias (creating the misleading impression that it was part of the recommendation rather than a specified part of the user's environment), and it didn't show how the wrapper would communicate with the called python script. In practice, the user would either have to source the wrapper or define the alias within the wrapper, and the python script would have to delegate the printing of error messages to multiple custom calling scripts (where the calling information resided), and clients would have to call the wrapper scripts. Solving those problems led to a simpler approach, that is expandable to any number of additional use cases.
Here's a less confusing version of the original script, for reference:
#!/bin/bash
shopt -s expand_aliases
alias myAlias='myPyScript.py'
# called like this:
set -o history
myAlias $#
_EXITCODE=$?
CALL_HISTORY=( `history` )
_CALLING_MODE=${CALL_HISTORY[1]}
case "$_EXITCODE" in
0) # no error message required
;;
1)
echo "customized error message #1 [$_CALLING_MODE]" 1>&2
;;
2)
echo "customized error message #2 [$_CALLING_MODE]" 1>&2
;;
esac
Here's the output:
$ aliasTest.sh 1 2 3
['./myPyScript.py', '1', '2', '3']
customized error message #2 [myAlias]
There is no way to distinguish between when an interpreter for a script is explicitly specified on the command line and when it is deduced by the OS from the hashbang line.
Proof:
$ cat test.sh
#!/usr/bin/env bash
ps -o command $$
$ bash ./test.sh
COMMAND
bash ./test.sh
$ ./test.sh
COMMAND
bash ./test.sh
This prevents you from detecting the difference between the first two cases in your list.
I am also confident that there is no reasonable way of identifying the other (mediated) ways of calling a command.
I can see two ways to do this:
The simplest, as suggested by 3sky, would be to parse the command line from inside the python script. argparse can be used to do so in a reliable way. This only works if you can change that script.
A more complex way, slightly more generic and involved, would be to change the python executable on your system.
Since the first option is well documented, here are a bit more details on the second one:
Regardless of the way your script is called, python is ran. The goal here is to replace the python executable with a script that checks if foo.py is among the arguments, and if it is, check if --bar is as well. If not, print the message and return.
In every other case, execute the real python executable.
Now, hopefully, running python is done trough the following shebang: #!/usr/bin/env python3, or trough python foo.py, rather than a variant of #!/usr/bin/python or /usr/bin/python foo.py. That way, you can change the $PATH variable, and prepend a directory where your false python resides.
In the other case, you can replace the /usr/bin/python executable, at the risk of not playing nice with updates.
A more complex way of doing this would probably be with namespaces and mounts, but the above is probably enough, especially if you have admin rights.
Example of what could work as a script:
#!/usr/bin/env bash
function checkbar
{
for i in "$#"
do
if [ "$i" = "--bar" ]
then
echo "Well done, you added --bar!"
return 0
fi
done
return 1
}
command=$(basename ${1:-none})
if [ $command = "foo.py" ]
then
if ! checkbar "$#"
then
echo "Please add --bar to the command line, like so:"
printf "%q " $0
printf "%q " "$#"
printf -- "--bar\n"
exit 1
fi
fi
/path/to/real/python "$#"
However, after re-reading your question, it is obvious that I misunderstood it. In my opinion, it is all right to just print either "foo.py must be called like foo.py --bar", "please add bar to your arguments" or "please try (instead of )", regardless of what the user entered:
If that's an (git) alias, this is a one time error, and the user will try their alias after creating it, so they know where to put the --bar part
with either with /usr/bin/foo.py or python foo.py:
If the user is not really command line-savvy, they can just paste the working command that is displayed, even if they don't know the difference
If they are, they should be able to understand the message without trouble, and adjust their command line.
I know it's bash task, but i think the easiest way is modify 'foo.py'. Of course it depends on level of script complicated, but maybe it will fit. Here is sample code:
#!/usr/bin/python
import sys
if len(sys.argv) > 1 and sys.argv[1] == '--bar':
print 'make magic'
else:
print 'Please add the --bar option to your command, like so:'
print ' python foo.py --bar'
In this case, it does not matter how user run this code.
$ ./a.py
Please add the --bar option to your command, like so:
python foo.py --bar
$ ./a.py -dua
Please add the --bar option to your command, like so:
python foo.py --bar
$ ./a.py --bar
make magic
$ python a.py --t
Please add the --bar option to your command, like so:
python foo.py --bar
$ /home/3sky/test/a.py
Please add the --bar option to your command, like so:
python foo.py --bar
$ alias a='python a.py'
$ a
Please add the --bar option to your command, like so:
python foo.py --bar
$ a --bar
make magic
I am trying to run multiple similar commands using a for loop and string formatting.
I am able to create and then print the strings of the commands I would like to run:
$foo=( "bar" "baz" )
$for ((j=0;j<2;++j)); do printf "touch %s_file.txt; " "${foo[j]}"; done
touch bar_file.txt; touch baz_file.txt;
But I want to enter these strings as a command. Based on other questions I was thinking that eval would do what I need:
$for ((j=0;j<2;++j)); do eval "touch %s_file.txt; " "${foo[j]}"; done
-bash: bar: command not found
-bash: baz: command not found
I was expecting(or hoping) the output would be equivalent to the output of:
$touch bar_file.txt; touch baz_file.txt;
The touch here is just an example. I'm more interested in how to format a string and then run it as a command. Thanks.
First, there's no need for using string formatting to generate code here, or in general -- BashFAQ #50 describes the use cases and better-practice alternatives. This could be as simple as the following:
for j in in "${foo[#]}"; do touch "${j}_file.txt"; done
Second, if you must, do it like so:
printf -v cmd 'touch %q_file.txt; ' "${foo[#]}"
eval "$cmd"
This will set cmd='touch bar_file.txt; touch baz_file.txt ', and then execute it.
Use of %q when content is to be later parsed by a shell (as with eval) ensures that your array elements are formatted in a way that will survive shell-parsing -- so if you had foo=( "name with spaces" 'name with $(rm -rf $HOME) dangerous content' ), you would be correctly touching 'name with spaces_file.txt' and 'name with $(rm -rf $HOME) dangerous content_file.txt', not executing the dangerous content and touching multiple files based on the spaces.
Instead of trying to put the whole command in a string, why not make a function to do the thing you want like:
update_file() {
touch "$1"
}
foo=( "bar" "baz" )
for ((j=0;j<2;++j)); do
update_file "$(printf "%s_file.txt" "${foo[j]}")"
done
then you can make that function do arbitrarily complex things with the files
As a general rule, variables hold data, not code. You can sometimes make it work putting code into data, but that way lies dragons. See here for some good reading on that
I want to create a bash script that is simular to a programming interpreter like mongo, node, redis-cli, mysql, etc.
I want to be able to use a command like test and it behave like the examples above.
thomas#workstation:~$ test
>
How do I make a command that behaves like this? What is this called?
I want to be able to take the content and turn it into a variable.
thomas#workstation:~$ test
> hello world
hello world
thomas#workstation:~$
I only want to take one "entry" after enter is pressed once I want to be able to process the string "hello world" in the code, like echo it.
What is this called? How do I make one using BASH?
I think "read" is what you are looking for, isn't it?
here is a link with some examples: http://bash.cyberciti.biz/guide/Getting_User_Input_Via_Keyboard
so you can do stuff like this:
read -p "Enter your name : " name
echo "Hi, $name. Let us be friends!"
I'm sorry this doesn't answer you directly, but it might be worth it to look into using a more fully capable programming language such as Python, Ruby, or Perl for a task like this. In Python you can use the raw_input() function.
user_command = raw_input('> ')
would yield your prompt.
First, do not name your script test. That generates too much confusion. Whatever you call it, you can do many things:
#!/bin/sh
printf '> '
read line
echo "$line"
If your shell supports it:
#!/bin/sh
read -p '> ' line
echo "$line"
or
#!/bin/sh
printf '> '
sed 1q # This will print the input. To store in in a variable: a=$( sed 1q )
[spatel#tux ~]$ read a
Hello World!!!!!
[spatel#tux ~]$ echo $a
Hello World!!!!!
Key word that might be useful here is REPL (Read–eval–print loop) used primarily for programming languages or coding environments. Your browsers console is a great example of a REPL.
Node allows you use their REPL to build interactive apps.
If I am writing a bash script, and I choose to use a config file for parameters. Can I still pass in parameters for it via the command line? I guess I'm asking can I do both on the same command?
The watered down code:
#!/bin/bash
source builder.conf
function xmitBuildFile {
for IP in "{SERVER_LIST[#]}"
do
echo $1#$IP
done
}
xmitBuildFile
builder.conf:
SERVER_LIST=( 192.168.2.119 10.20.205.67 )
$bash> ./builder.sh myname
My expected output should be myname#192.168.2.119 and myname#10.20.205.67, but when I do an $ echo $#, I am getting 0, even when I passed in 'myname' on the command line.
Assuming the "config file" is just a piece of shell sourced into the main script (usually containing definitions of some variables), like this:
. /etc/script.conf
of course you can use the positional parameters anywhere (before or after ". /etc/..."):
echo "$#"
test -n "$1" && ...
you can even define them in the script or in the very same config file:
test $# = 0 && set -- a b c
Yes, you can. Furthemore, it depends on your architecture of script. You can overwrite parametrs with values from config and vice versa.
By the way shflags may be pretty useful in writing such script.