I'm trying to set "fzf - Fuzzy finder for your shell" for the fish shell. The problem is that interactive commands don't work when I use it in command substitution. Example:
This command works: (echoes all the files in the current dir, and I can interactively select one by fuzzy-finder)
ls | fzf
But this one doesn't work:
echo (ls | fzf)
It just immediately returns empty string.
It doesn't work for any interactive command, so if you haven't fzf, you can test it with, say, off the top of my head, chsh:
This command works: (asks for password)
chsh
but this one doesn't: (immediately returns empty string)
echo (chsh)
More, when I try to exit fish, it says that "there are stopped jobs", i.e. interactive command starts and immediately stops.
How to make it work?
This is probably just a bug. See https://github.com/fish-shell/fish-shell/issues/1362 (as discussed on the mailing list)
Related
I wrote simple command that lets me run the last N commands from terminal history. It looks like this: $> r 3 which will replay the last 3 commands.
I have the following alias in my bash profile:
alias r="history -w; runlast $1"
And then the following simple perl script for the runlast command:
#!/usr/bin/env perl
use strict;
use warnings;
my $lines = $ARGV[0] || exit;
my #last_commands = split /\n/,
`bash -ic 'set -o history; history' | tail -$lines`;
#last_commands =
grep { $_ !~ /(^r |^history |^rm )/ }
map { local $_ = $_; s/^\s+\d+\s+//; $_ }
#last_commands;
foreach my $cmd (#last_commands) {
system("$cmd");
}
This works but my bash profile has aliases and other features (e.g. color output) I want the perl script to have access to. How do I load the bash profile for perl so it runs the bash commands with my bash profile? I read somewhere that if you "source the bash profile" for perl you can get it to work. So I tried adding source ~/.bash_profile; to my r command alias but that didn't have an effect. I'm not sure if I was doing that correctly, though.
The system forks a process in which it runs a shell, which is non-login and non-interactive; so no initialization is done and you get no aliases. Also note that the shell used is /bin/sh, which is generally a link to another shell. This is often bash but not always, so run bash explicitly.
To circumvent this you need to source the file with aliases, but as bash man page says
Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt (see the description of shopt under SHELL BUILTIN COMMANDS below).
Thus you need shopt -s expand_aliases, as mentioned. But there is another screw: on that same physical line aliases are not yet available; so it won't work like this in a one-liner.
I'd also recommend to put aliases in .bashrc, or in a separate file that is sourced.
Solutions
Add shopt -s expand_aliases to your ~/.bashrc, and before the aliases are defined (or the file with them sourced), and run bash as a login shell
system('/bin/bash', '-cl', 'source ~/.bashrc; command');
where -l is short for --login.
In my tests the source ~/.bashrc wasn't needed; however, the man page says
When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable.
and goes on to specify that ~/.bashrc is read when an interactive shel that is not login runs. So I added explicit sourcing.
In my tests sourcing .bashrc (with shopt added) while not running as a login shell didn't work, and I am not sure why.
This is a little heavy-handed. Also, initialization may be undesirable to run from a script.
Source ~/.bashrc and issue shopt command, and then a newline before the command
system('/bin/bash', '-c',
'source ~/.bashrc; shopt -s expand_aliases\ncommand');
Really. It works.
Finally, is this necessary? It asks for trouble, and there is probably a better design.
Other comments
The backticks (qx) is context-aware. If it's used in list context – its return assigned to an array, for example – then the command's output is returned as a list of lines. When you use it as the argument for split then it is in the scalar context though, when all output is returned in one string. Just drop split
my #last_commands = `bash -ic 'set -o history; history $lines`;
where I also use history N to get last N lines. In this case the newlines stay.
history N returns last N lines of history so there is no need to pipe to last
Regex substitution in a map can be done without changing the original
map { s/^\s+\d+\s+//r } #last_commands;
With /r modifier the s/// operator returns the new string, not changing the original. This "non-destructive substitution" has been available since v5.14
No need to explicitly use $_ in the last grep, and no need for parenthesis in regex
grep { not /^r |^history |^rm ?/ } ...
or
grep { not /^(?:r|history|rm)[ ]?/ } ...
where parens are now needed, but as it is only for grouping the ?: makes it not capture the match. I use [ ] to emphasize that that space is intended; this is not necessary.
I also added ? to make space optional since history (and r?) may have no space.
The proper solution is to have your Perl script just print the commands, and make your current interactive shell eval the string printed from your history. (I would probably get rid of Perl entirely but that's beside the point here.)
If the commands get evaluated in the current shell, you avoid many contextual problems which would be very hard or even intractable with system() or generally anything involving a new process. For example, a subprocess cannot have access to non-exported variables in the current shell. var="foo", echo "$var"; r 1 is going to be very hard to solve correctly with your current approach. Using the current interactive shell will also naturally and easily solve the problems you were having with trying to get a noninteractive subshell act like an interactive one.
Aliases suck anyway, so let's redefine r as a function:
r(){
history -w
eval $(printlast "$1")
}
... where refactoring runlast into a different script printlast is a trivial additional requirement. Or maybe just turn it into a (much simpler!) shell function:
printlast () {
history "$1" |
perl -ne 's/^\s*\d+\s+\*?//; print unless m/^(history|rm?)($|\s)'
}
With this, you can also get rid of history -w from the r definition.
Notice how we are using Perl where it is useful; but the main functionality makes sense to keep in the shell when you're dealing with the shell.
You can't source in a Bash script into a Perl script. The bash_profile has to be sourced in by the shell that executes the command. When Perl runs system, it forks a new shell each time.
You have to source in the bash_profile for each command that you run through system:
system('source ~/.bash_profile; ' + $cmd);
One more thing, system invokes a non-interactive shell. So, your Bash aliases defined in .bash_profile won't work unless you invoke:
shopt -s expand_aliases
inside that script
I'm trying to get last executed command from command line from a script to be saved for a later reference:
Example:
# echo "Hello World!!!"
> Hello World!!!
# my_script.sh
> echo "Hello World!!!"
and the content of the script would be :
#!/usr/bin/ksh
fc -nl -1 | sed -n 1p
Now as you notices using here ksh and fc is a built in command which if understood correctly should be implemented by any POSIX compatible shells. [I understand that this feature is interactive and that calling same fc again will give different result but this is not the concern do discuss about]
Above works so far so good only if my_script.sh is being called from the shell which is as well ksh, or if calling from bash and changing 1st line of script as #!/bin/bash then it works too and it doesn't if shells are different.
I would like to know if there is any good way to achieve above without being constrained by the shell your script is called from. I understand that fc is a built in command and it works per shell thus most probably my approach is not good at all from what I want to achieve. Any better suggestions?
I actually attempted this, but it cannot be done between different shells consistently.
While
fc -l`,
is the POSIX standard command for showing $SHELL history, implementation details may be different.
At least bash and ksh93 both will report the last command with
fc -n -l -1 -1
However, POSIX does not guarantee that shell history will be carried over to a new instance of the shell, as this requires the presence of a $HISTFILE. If none is
present, the shell may default to $HOME/.sh_history.
However, this history file or Command History List is not portable between different shells.
The POSIX Shell description of the
Command History List says:
When the sh utility is being used interactively, it shall maintain a list of commands
previously entered from the terminal in the file named by the HISTFILE environment
variable. The type, size, and internal format of this file are unspecified.
Emphasis mine
What this means is that for your script needs to know which shell wrote that history.
I tried to use $SHELL -c 'fc -nl -1 -1', but this did not appear to work when $SHELL refers to bash. Calling ksh -c ... from bash actually worked.
The only way I could get this to work is by creating a function.
last_command() { (fc -n -l -1 -1); }
In both ksh and bash, this will give the expected result. Variations of this function can be used to write the result elsewhere. However, it will break whenever it's called
from a different process than the current.
The best you can do is to create these functions and source them into your
interactive shell.
fc is designed to be used interactively. I tested your example on cygwin/bash and the result was different. Even with bash everywhere the fc command didn't work in my case.
I think fc displays the last command of the current shell (here I don't speak about the shell interpretor, but shell as the "process box". So the question is more why it works for you.
I don't think there is a clean way to achieve what you want because (maybe I miss something) you want two different process (bash and your magic command [my_script.sh]) and by default OS ensure isolation between them.
You can rely on what you observe (not portable, depends on the shell interpretor etc.)
You cannot rely on BASH historic because it's in-memory (the file is updated only on exit).
You can use an alias or a function (edited: #Charles Duffy is right). In this case you won't be able to use your "magic command" from another terminal, but for an interactive use it does the job.
Edited:
Or you can provide two commands: one to save and another to look for. In this case you manage your own historic but you have to save explicitly each command that is painful...
So I look for a hook. And I found this other thread : https://superuser.com/questions/175799/does-bash-have-a-hook-that-is-run-before-executing-a-command
# At the beginning of the Shell (.bashrc for example)
save(){ history 1 >>"$HOME"/myHistory ; }
trap 'save' DEBUG
# An example of use
rm -f "$HOME"/myHistory
echo "1 2 3"
cat "$HOME"/myHistory
14 echo "1 2 3"
15 cat "$HOME"/myHistory
But I observe it slows down the interpretor...
Little convoluted, but I was able to use this command to get the most recent command in zsh, bash, ksh, and tcsh on Linux:
history | tail -2 | head -1 | sed -r 's/^[ \t]*[0-9]*[ \t]+([^ \t].*$)/\1/'
Caveats: this uses GNU sed, so you'll need to install that if you're using BSD, OS X, etc; and also, tcsh will display the time of the command before the command itself. Regular csh doesn't seem to having a functioning history command when I tried it.
Can anyone tell me what are login shell and interactive shell and which configurations each of them read(etc/profile, etc/bashrc, .bash_profile ...)??
I saw some explanation like this:
A login shell is one whose first character of argument zero is a -, or
one started with the --login option.
An interactive shell is one started without non-option arguments and
without the -c option whose standard input and error are both connected
to terminals (as determined by isatty(3)), or one started with the -i
option. PS1 is set and $- includes i if bash is interactive, allowing
a shell script or a startup file to test this state.
But this confused more !!!
The man bash command on your system (INVOCATION section) talks about all of this and it describes which files are read when.
Well, if you don't trust the manual page, try using strace.
strace -o/tmp/tr -f bash
exit
grep open /tmp/tr | grep $HOME
For me, this shows:
18316 open("/home/sethrobertson/.bashrc", O_RDONLY) = 3
What does it show for you?
Why doesn't the following work?
$ alias sayHello='/bin/echo "Hello world!"'
$ sayHello
Hello world!
$ nohup sayHello
nohup: appending output to `nohup.out'
nohup: cannot run command `sayHello': No such file or directory
(the reason I ask this question is because I've aliased my perl and python to different perl/python binaries which were optimized for my own purposes; however, nohup gives me troubles if I don't supply full path to my perl/python binaries)
Because the shell doesn't pass aliases on to child processes (except when you use $() or ``).
$ alias sayHello='/bin/echo "Hello world!"'
Now an alias is known in this shell process, which is fine but only works in this one shell process.
$ sayHello
Hello world!
Since you said "sayHello" in the same shell it worked.
$ nohup sayHello
Here, a program "nohup" is being started as a child process. Therefore, it will not receive the aliases.
Then it starts the child process "sayHello" - which isn't found.
For your specific problem, it's best to make the new "perl" and "python" look like the normal ones as much as possible. I'd suggest to set the search path.
In your ~/.bash_profile add
export PATH="/my/shiny/interpreters/bin:${PATH}"
Then re-login.
Since this is an environment variable, it will be passed to all the child processes, be they shells or not - it should now work very often.
For bash: Try doing nohup 'your_alias'. It works for me. I don't know why back quote is not shown. Put your alias within back quotes.
With bash, you can invoke a subshell interactively using the -i option. This will source your .bashrc as well as enable the expand_aliases shell option. Granted, this will only work if your alias is defined in your .bashrc which is the convention.
Bash manpage:
If the -i option is present, the shell is interactive.
expand_aliases: If set, aliases are expanded as described above under ALIASES. This option is enabled by default for interactive shells.
When an interactive shell that is not a login shell is started, bash reads and executes commands from /etc/bash.bashrc and ~/.bashrc, if these files exist.
$ nohup bash -ci 'sayHello'
If you look at the Aliases section of the Bash manual, it says
The first word of each simple command, if unquoted, is checked to see
if it has an alias.
Unfortunately, it doesn't seem like bash has anything like zsh's global aliases, which are expanded in any position.
I have a bash script where I trap errors using the trap command, and I would like to be able to print the name of the last command (the one that failed)
#!/bin/bash
function error
{
# echo program name
}
trap error ERR
# Some commands ...
/bin/false foo # For testing
I'm not sure what to put in the error function. I tried echo $_ but that only works if the command has no arguments. I also tried with !! but that gives me "!!: command not found". At an interactive prompt (also bash) I get:
$ /bin/false foo
$ !!
/bin/false foo
which seems to be pretty much what I want. Why the difference?
What is the easiest way to get the name of the previous command inside a script?
Try echo $BASH_COMMAND in your trap function.
From man bash:
BASH_COMMAND
The command currently being executed or about to be executed,
unless the shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the
trap.
You need to set
set -o history
to quote bash manual page:
When the -o history option to the set builtin is enabled, the shell provides access to the command history, the list of commands previously typed. The value of the HISTSIZE variable is used
as the number of commands to save in a history list. The text of the last HISTSIZE commands (default 500) is saved. The shell stores each command in the history list prior to parameter and
variable expansion (see EXPANSION above) but after history expansion is performed, subject to the values of the shell variables HISTIGNORE and HISTCONTROL.
In general, read the HISTORY and HISTORY EXPANSION sections in bash man page.