This question is in addition to the question asked here: https://unix.stackexchange.com/questions/163145/how-to-get-whole-command-line-from-a-process. On my system, the following command results in a PID (as expected):
CUDA_VISIBLE_DEVICES=4,5 python3 main.py 1> out.txt 2> err.txt &
Now, the methods in the stack exchange link above provide many solutions. However, when trying these solutions, I only receive the following information:
python3 main.py
Is there a way to return the entire command line "CUDA_VISIBLE_DEVICES=4,5 python3 main.py 1> out.txt 2> err.txt &", not just the portion "python3 main.py"?
No.
Assuming you're on a Linux system, you can find the individual bits, but you can't put it together.
Assume also that the process's PID is in $pid
The CUDA_VISIBLE_DEVICES=4,5 variable gets added to the environment of the python command. You can find it in /proc/$pid/environ but you can't tell which of those variables were specified on the command line: the user could have written
export CUDA_VISIBLE_DEVICES=4,5
python3 main.py 1> out.txt 2> err.txt &
The file redirections are available in /proc/$pid/fd:
/proc/$pid/fd/1 is a symbolic link to out.txt
/proc/$pid/fd/2 is a symbolic link to err.txt
I don't know how to tell if a process is running in the background.
Since you're just interested in the environment: with bash
declare -A environ
while IFS='=' read -r -d '' var value; do
environ["$var"]="$value"
done < /proc/$pid/environ
echo "process has CUDA_VISIBLE_DEVICE value ${environ[CUDA_VISIBLE_DEVICE]}"
Related
I have a script where I need to start a command, then pass some additional commands as commands to that command. I tried
su
echo I should be root now:
who am I
exit
echo done.
... but it doesn't work: The su succeeds, but then the command prompt is just staring at me. If I type exit at the prompt, the echo and who am i etc start executing! And the echo done. doesn't get executed at all.
Similarly, I need for this to work over ssh:
ssh remotehost
# this should run under my account on remotehost
su
## this should run as root on remotehost
whoami
exit
## back
exit
# back
How do I solve this?
I am looking for answers which solve this in a general fashion, and which are not specific to su or ssh in particular. The intent is for this question to become a canonical for this particular pattern.
Adding to tripleee's answer:
It is important to remember that the section of the script formatted as a here-document for another shell is executed in a different shell with its own environment (and maybe even on a different machine).
If that block of your script contains parameter expansion, command substitution, and/or arithmetic expansion, then you must use the here-document facility of the shell slightly differently, depending on where you want those expansions to be performed.
1. All expansions must be performed within the scope of the parent shell.
Then the delimiter of the here document must be unquoted.
command <<DELIMITER
...
DELIMITER
Example:
#!/bin/bash
a=0
mylogin=$(whoami)
sudo sh <<END
a=1
mylogin=$(whoami)
echo a=$a
echo mylogin=$mylogin
END
echo a=$a
echo mylogin=$mylogin
Output:
a=0
mylogin=leon
a=0
mylogin=leon
2. All expansions must be performed within the scope of the child shell.
Then the delimiter of the here document must be quoted.
command <<'DELIMITER'
...
DELIMITER
Example:
#!/bin/bash
a=0
mylogin=$(whoami)
sudo sh <<'END'
a=1
mylogin=$(whoami)
echo a=$a
echo mylogin=$mylogin
END
echo a=$a
echo mylogin=$mylogin
Output:
a=1
mylogin=root
a=0
mylogin=leon
3. Some expansions must be performed in the child shell, some - in the parent.
Then the delimiter of the here document must be unquoted and you must escape those expansion expressions that must be performed in the child shell.
Example:
#!/bin/bash
a=0
mylogin=$(whoami)
sudo sh <<END
a=1
mylogin=\$(whoami)
echo a=$a
echo mylogin=\$mylogin
END
echo a=$a
echo mylogin=$mylogin
Output:
a=0
mylogin=root
a=0
mylogin=leon
A shell script is a sequence of commands. The shell will read the script file, and execute those commands one after the other.
In the usual case, there are no surprises here; but a frequent beginner error is assuming that some commands will take over from the shell, and start executing the following commands in the script file instead of the shell which is currently running this script. But that's not how it works.
Basically, scripts work exactly like interactive commands, but how exactly they work needs to be properly understood. Interactively, the shell reads a command (from standard input), runs that command (with input from standard input), and when it's done, it reads another command (from standard input).
Now, when executing a script, standard input is still the terminal (unless you used a redirection) but the commands are read from the script file, not from standard input. (The opposite would be very cumbersome indeed - any read would consume the next line of the script, cat would slurp all the rest of the script, and there would be no way to interact with it!) The script file only contains commands for the shell instance which executes it (though you can of course still use a here document etc to embed inputs as command arguments).
In other words, these "misunderstood" commands (su, ssh, sh, sudo, bash etc) when run alone (without arguments) will start an interactive shell, and in an interactive session, that's obviously fine; but when run from a script, that's very often not what you want.
All of these commands have ways to accept commands by ways other than in an interactive terminal session. Typically, each command supports a way to pass it commands as options or arguments:
su root -c 'who am i'
ssh user#remote uname -a
sh -c 'who am i; echo success'
Many of these commands will also accept commands on standard input:
printf 'uname -a; who am i; uptime' | su
printf 'uname -a; who am i; uptime' | ssh user#remote
printf 'uname -a; who am i; uptime' | sh
which also conveniently allows you to use here documents:
ssh user#remote <<'____HERE'
uname -a
who am i
uptime
____HERE
sh <<'____HERE'
uname -a
who am i
uptime
____HERE
For commands which accept a single command argument, that command can be sh or bash with multiple commands:
sudo sh -c 'uname -a; who am i; uptime'
As an aside, you generally don't need an explicit exit because the command will terminate anyway when it has executed the script (sequence of commands) you passed in for execution.
If you want a generic solution which will work for any kind of program, you can use the expect command.
Extract from the manual page:
Expect is a program that "talks" to other interactive programs according to a script. Following the script, Expect knows what can be expected from a program and what the correct response should be. An interpreted language provides branching and high-level control structures to direct the dialogue. In addition, the user can take control and interact directly when desired, afterward returning control to the script.
Here is a working example using expect:
set timeout 60
spawn sudo su -
expect "*?assword" { send "*secretpassword*\r" }
send_user "I should be root now:"
expect "#" { send "whoami\r" }
expect "#" { send "exit\r" }
send_user "Done.\n"
exit
The script can then be launched with a simple command:
$ expect -f custom.script
You can view a full example in the following page: http://www.journaldev.com/1405/expect-script-example-for-ssh-and-su-login-and-running-commands
Note: The answer proposed by #tripleee would only work if standard input could be read once at the start of the command, or if a tty had been allocated, and won't work for any interactive program.
Example of errors if you use a pipe
echo "su whoami" |ssh remotehost
--> su: must be run from a terminal
echo "sudo whoami" |ssh remotehost
--> sudo: no tty present and no askpass program specified
In SSH, you might force a TTY allocation with multiple -t parameters, but when sudo will ask for the password, it will fail.
Without the use of a program like expect any call to a function/program which might get information from stdin will make the next command fail:
ssh use#host <<'____HERE'
echo "Enter your name:"
read name
echo "ok."
____HERE
--> The `echo "ok."` string will be passed to the "read" command
I'm using PostgreSQL on Windows 7 through the command line. I want to import the content of different CSV files into a newly created table.
After executing the command the database name appeared like:
database=#
Now appears like
database*# after executing:
type directory/*.csv | psql -c 'COPY sch.trips(value1, value2) from stdin CSV HEADER';
What does *# mean?
Thanks
This answer is for Linux and as such doesn't answer OP's question for Windows. I'll leave it up anyway for anyone that comes across this in the future.
You accidentally started a block comment with your type directory/*.csv. type doesn't do what you think it does. From the bash built-ins:
With no options, indicate how each name would be interpreted if used as a command name.
Try doing cat instead:
cat directory/*.csv | psql -c 'COPY sch.trips(value1, value2) from stdin CSV HEADER';
If this gives you issues because each CSV has its own header, you can also do:
for file in directory/*.csv; do cat "$file" | psql -c 'COPY sch.trips(value1, value2) from stdin CSV HEADER'; done
Type Command
The type built-in command in Bash is a way of viewing command interpreter results. For example, using it with ssh:
$ type ssh
ssh is /usr/bin/ssh
This indicates how ssh would be interpreted when you run ssh as a command in the current Bash environment. This is useful for things like aliases. As an example for this, ll is usually an alias to ls -l. Here's what my Bash environment had for ll:
$ type ll
ll is aliased to `ls -l --color=auto'
For you, when you pipe the result of this command to psql, it encounters the /* in the input and assumes it's a block comment, which is what the database*# prompt means (the * indicates it's waiting for the comment close pattern, */).
Cat Command
cat is for concatenating multiple files together. By default, it writes to standard out, so cat directory/*.csv will write each CSV file to standard out one after another. However, piping this means that each CSV's header will also be piped mid-stream of the copy. This may not be desirable, so:
For Loop
We can use for to loop over each file and individually import it. The version I have above, for file in directory/*.csv, will properly handle files with spaces. Properly formatted:
for file in directory/*; do
cat "$file" | psql -c 'COPY sch.trips(value1, value2) from stdin CSV HEADER'
done
References
PostgreSQL 10 Comments Documentation (postgresql.org)
type built-in Manual page (mankier.com)
cat Manual page (mankier.com)
Bash looping tutorial (tldp.org)
The IPython 0.13.1 documentation says:
$ ipython -h
...
Usage
ipython [subcommand] [options] [files]
If invoked with no options, it executes all the files listed in sequence
and exits, use -i to enter interactive mode after running the files.
...
I have two files foo.py and bar.py.
foo.py:
print "Hi, I'm foo."
bar.py:
print "Hi, I'm bar."
I expect the following to print both files output, in the corresponding order. Instead I only get the output from the first file given on the command line.
$ ipython foo.py bar.py
Hi, I'm foo.
$ ipython bar.py foo.py
Hi, I'm bar.
Is that an implementation bug, a documentation bug, or user misunderstanding? If the latter, what should I do instead?
This is a documentation failure, fixed by this Pull Request.
The command
$> ipython [-i] script.py script2.py ...
behaves exactly the same as the command
$> python [-i] script.py script2.py ...
In that, script.py is run, with sys.argv of ['script.py', 'script2.py', '...'],
and if -i is specified, it drops into an interactive session after running the script.
I am trying to see what exact command line arguments are being sent to scanimage from xsane. I tried ltrace but couldn't find "scanimage" anywhere in the log. In general, suppose you know some GUI program is a frontend of a command line pro
If xsane call scanimage, you will find that by replacing the scanimage executable by this script temporarily :
#!/bin/bash
exec &>/tmp/trace
echo "$0" "$#"
Then,
chmod +x /usr/bin/scanimage
xsane
cat /tmp/trace
Can sh itself check if a program exists or is in path?
I.e., not with the help of the "which" program.
I don't believe sh can directly. But perhaps something like:
which() {
save_IFS=$IFS
IFS=:
for d in $PATH; do
test -x $d/$1 && echo $d/$1
done
IFS=$save_IFS
}
and here's a nice variation that uses a subshell so that restoring IFS is not necessary:
which() (
IFS=:
for d in $PATH; do
test -x $d/$1 && echo $d/$1
done
)
Also, (in bash) if the command has been executed in the past and bash has already done the PATH search, you can see what it found with hash -t.
bash-3.2$ hash -t which
bash: hash: which: not found
bash-3.2$ which foo
bash-3.2$ hash -t which
/usr/bin/which
The utility command -v $CMD is apparently a portable option (in the sense of being part of POSIX); see also the very similar (though bash-specific) question, in particular this answer.