modifying previously executed commands on linux - linux

I want to modify a previously run command with slightly different arguments. Is there a quick way of reaching the argument which is somewhere between in the big command, instead of going to that place from beginning (or end) of the command?
Currently I wrap the big command into some small command and pass the argument to the wrapper command.
Was wondering if there was any other way.

You can press ↑ to bring the last line;
Then you can jump over the arguments with Alt+F and Alt+B.
(if you're on Mac it's Esc+F and Esc+B)
You may also type !:1 to refer to the first argument in the previous entry, or !:2 to refer to the second argument, and so on.

Related

vim: Run multiple commands based off of one :global command

Apologies if this has been posted already, for I cannot find an answer, even on the vim wiki.
Is there a way I can run multiple commands in vim command-line mode off of a single :g search?
For example,
:%g/foo/ s/bar/\=#a/g | exe "norm /cat\<enter>\"ayiw"
Which (for what I intend it to do) should, on every line matching foo, replace bar with the contents of register a, and then find the next iteration of cat (even if it is many lines ahead), and put the surrounding word into register a.
Instead, this specific syntax completes the subsitution command using the current contents of the initial a register, and then executes the normal mode command on a single line (after the substitution has been completed).
This example is not my specific use-case but shows one instance where this functionality is useful. I realize I could put it all into a single exe, i.e., %g/foo/exe "norm :s/bar/\\=#a/g\<enter>/cat\<enter>\"ayiw", but I would like to do it the first way, as I feel it is more flexible.
I would prefer to do this using vanilla vim, but if a plugin exists for this, that is an okay alternative. Does anybody know if there is syntax to do such a thing?
Okay a "little bit" dirty, but does this work for you?
:let list = split(execute('g/cat/p'), '\n') | g/foo/ s/bar/\=matchstr(remove(list, 0), '\s\d\+\s\zs.*')/g
It first reads all occurences of cat save them in a list.
Then replace the first bar with the first cat... and so on.
The dirty part ist the matchstr command. the g//p also returns a number for the result so the list looks like this:
1 cat
2 cat
3 cat
...
that's why we have to remove a bit from the front. I would love to hear if someone knows a clean solution for that (I am also interested in a clean vimscript solution, does not have to be a oneliner).
You can do this (at least for multiple :s commands applied to a single :g). Example:
" SHORT STORY TITLES to single word of CapitalizedWords within <h3>s
.,$g/^\L\+$/s/[^A-Z0-9 ]\+//ge|s/\u\+/\L&/ge|s/\<\l\+\>/\u&/ge|s/ \+//ge|s/.*/<h3>&<\/h3>/

How to accept the 'Did you mean?' terminal/git suggestion

This is a simple question.
Sometimes on a Terminal when you make a small mistake the console asks ¿Did you mean ...? - ¿Is there a way to quicky accept the suggestion?.
For example:
$ git add . -all
error: did you mean `--all` (with two dashes ?)
Is there a command that repeats the last line, but with the two dashes?
If you forget to write sudo, you can just do sudo !! and it will solve your problem. I want to know if there is something similar but for the error: did you mean case.
In the case of...
$ git add . -all
error: did you mean `--all` (with two dashes ?)
...the message is written by git directly to the terminal. This means that bash has no way of knowing what message was written; it would be literally impossible to implement anything in the shell that could automate putting that correction in place without making programs run under the shell considerably less efficient (by routing their output through the shell rather than directly to the terminal) and changing their behavior (if they ever call isatty() on their stdout or stderr).
That said, you can certainly run
^-all^--all
...if you haven't turned history expansion off, as with set +H (if off, it can be reenabled with set -H). I typically do turn this functionality off, myself; it's often more trouble than it's worth (making commands which would work perfectly well in scripts break in interactive shells when they use characters that history expansion is sensitive to, particularly !).

Using bash history to get a previous command, copy it and then 'run' it but with the command commented

Just a question to improve my bash skills. I always do this:
$ history | grep some_long_command
...
...
123 some_long_command1.........
124 some_long_command2.........
...
I can then run the command the command I found by doing:
!123
However, I often want to do this:
some_long_command1foobar
I.e. change the command before I run it. Can you use bash to run this command instead:
#some_long_command1
so it gets commented.
Then I don't have to use my mouse to highlight the command, edit it and then run it (I can just use the keyboard - faster).
I suppose I could write a script to do it but there might already be functionality built in somewhere....?
I'd suggest instead of using the history command, you use ctrl+r and start typing that command. When you press an arrow key as if to go to modify it, it will drop out of autocomplete recognition, and will let you edit before running.
UPDATE: also, if you want to cycle through the different commands that contain the string you just typed, keep on pressing ctrl+r
Actually, you can just append :p to the command to print it without actually running it. For example:
$ ls -la
$ !!:p
Will print out ls -la as the previous command without running it, and you can just press ↑ (up) to find it and edit it.
You can also do
!123:p
to print out the 123rd command as your previous command.
You can also try fc command to edit the command in the history.
WIKI says,
​fc​ is a standard program on Unix that lists or edits and reexecutes,
commands previously entered to an interactive shell. fc is a built-in
command in the bash shell; help fc will show usage information.
Apart from reverse-incremental search(Ctrl+R), we have some more bash shortcuts:
From man bash:
previous-history (C-p)
Fetch the previous command from the history list, moving back in the list.
next-history (C-n)
Fetch the next command from the history list, moving forward in the list.
beginning-of-history (M-&lt)
Move to the first line in the history.
end-of-history (M->)
Move to the end of the input history, i.e., the line currently being entered.
reverse-search-history (C-r)
Search backward starting at the current line and moving 'up' through the history as necessary. This is an incremental search.
forward-search-history (C-s)
Search forward starting at the current line and moving 'down' through the history as necessary. This is an incremental search.
non-incremental-reverse-search-history (M-p)
Search backward through the history starting at the current line using a non-incremental search for a string supplied by the user.
non-incremental-forward-search-history (M-n)
Search forward through the history using a non-incremental search for a string supplied by the user.
yank-nth-arg (M-C-y)
Insert the first argument to the previous command (usually the second word on the previous line) at point. With an argument n, insert the nth word from the previous command (the words in the previous command begin with word 0). A negative argument inserts the nth word from the end of the previous command. Once the argument n is computed, the argument is extracted as if the "!n" history expansion had been specified.
yank-last-arg (M-., M-_)
Insert the last argument to the previous command (the last word of the previous history entry). With an argument, behave exactly like yank-nth-arg. Successive calls to yank-last-arg move back through the history list, inserting the last argument of each line in turn. The history expansion facilities are used to extract the last argument, as if the "!$" history expansion had been specified.
shell-expand-line (M-C-e)
Expand the line as the shell does. This performs alias and history expansion as well as all of the shell word expansions. See HISTORY EXPANSION below for a description of history expansion.
history-expand-line (M-^)
Perform history expansion on the current line. See HISTORY EXPANSION below for a description of history expansion.
insert-last-argument (M-., M-_)
A synonym for yank-last-arg.
operate-and-get-next (C-o)
Accept the current line for execution and fetch the next line relative to the current line from the history for editing. Any argument is ignored.
edit-and-execute-command (C-xC-e)
Invoke an editor on the current command line, and execute the result as shell commands.
!123:gs/old/new/
Will run command 123 replacing the string 'old' with the string 'new'.
You can get to edit mode by hitting M-^ (option-shift-6 on a mac).
Type this:
!123M-^
And you'll be editing command #123. It's sort of like using ctrl-r, but starting with exclamation-point syntax.
Instead of using the history command, bind history-search-backward/history-search-forward to key shortcuts which can be remembered easily (I prefer PgUp/PgDown). To do that, put this into your .inputrc file:
"<key code>": history-search-backward
"<key code>": history-search-forward
To get <key code>, type Ctrl-V <key> in the shell, and replace the starting ^[ with \e in whatever was output.
After this is set up, you can just type some and press PgUp to get some_long_command. If you need some_long_command with_some_arg but there is a similar command some_long_command with_some_other_arg later in the history, you can cycle through until you reach it by typing some and then hitting PgUp repeatedly, or you can type some, hit PgUp, move the cursor to where the two commands start to differ, type a few characters and hit PgUp once more. This ability to quickly page through / differentiate between similar commands makes it in my opinion a much more comfortable tool than Ctrl-R.
You can also put
shopt -s histverify
in your .bash_profile, which causes any history expansion to appear on your command line without running it, allowing you to edit before doing so.
You may wan to try "suggest box"-like history https://github.com/dvorka/hstr - it reads Bash history and allows for quick navigation.
To get the last command simply type hh, navigate to the command and use right arrow to get it on command line (where you can edit it and/or add comment).
^p to get the last typed command in unix/solaris
Put
alias r='fc -s'
in your .bashrc (home dir)
then you can just type in
r <whatever>
at the command prompt and you will execute a copy of the last <whatever> command (same params) that is in your history. just hit up arrow to see what you have executed if you feel the need.

The `:bar` in vim doesn't work as expected

After reading the vim doc about *:bar* *:\bar*:
'|' can be used to separate commands, so you can give multiple commands in one line.
I tried to clear history via this command:
:set history=0 | set history=20
I expect that, these two commands should be executed one by one, and the history should be cleared.
But it didn't. The history still there, and a new history was added.
Then I tried:
:set history=0
:set history=20
It works.
Why?
When you execute a command line that is what happens:
History is initialized (truncation happens here) (init_hist() function call in getcmdline()).
String to be executed is obtained (in getcmdline()).
It is added to history (add_to_history() call in getcmdline()).
It is executed (do_one_cmd() in do_cmdline(), happens after getcmdline() call (called by getexline() passed as fgetline argument to do_cmdline())).
Setting the option itself does nothing, it only changes p_hi variable. Actual modification of history is done at step 1.
Now let’s see what happens in both cases (assuming that you typed second or third additional command):
History is first initialized when p_hi has old value, then it is changed two times and then when you do next command it is already set to 20.
History is first initialized when p_hi has old value, then it is changed once and initialized for the second time, being effectively truncated at this step and only then the value changes again. By the time you start typing third command it is already wiped out.
Thus your assumption (commands are executed one by one) is true, but you have mistaken at which point history modification happens. I would rather suggest using histdel() as #Michael advised because, at first, it clears history by itself and, at second, it does not have hardcoded 'history' value. I can’t say how you live with just 20 lines long history (I’ve set it to 65535 and am always sure I won’t lose anything small, but useful), but hardcoding this value will make changing history size to something else more painful.

exec() security

I am trying to add security of GET query to exec function.
If I remove escapeshellarg() function, it work fine. How to fix this issue?
ajax_command.php
<?php
$command = escapeshellarg($_GET['command']);
exec("/usr/bin/php-cli " . $command);
?>
Assume $_GET['command'] value is run.php -n 3
What security check I can also add?
You want escapeshellcmd (escape a whole command, or in your case, sequence of arguments) instead of escapeshellarg (escape just a single argument).
Notice that although you have taken special precautions, this code allows anyone to execute arbitrary commands on your server anyways, by specifying the whole php script in a -r option. Note that php.ini can not be used to restrict this, since the location of it can be overwritten with -c. In short (and with a very small error margin): This code creates a severe security vulnerability.
escapeshellarg returns a quoted value, so if it contains multiple arguments, it won't work, instead looking like a single stringesque argument. You should probably look at splitting the command up into several different parameters, then each can be escaped individually.
It will fail unless there's a file called run.php -n 3. You don't want to escape a single argument, you want to escape a filename and arguments.
This is not the proper way to do this. Have a single PHP script run all your commands for you, everything specified in command line arguments. Escape the arguments and worry about security inside that PHP file.
Or better yet, communicate through a pipe.

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