I'm trying to set the cursor in place to make an autocompletion later in prompt, but I'm not achieving the desired result. The action goes like this:
First, I define a variable to expand like a command I use very often
my_command="script_name parameter1 /some/path/ parameterN"
As I want to place the cursor at the end of /some/path/ then I define another variable as:
set_cursor='$my_command; $(echo -en "\033[10D")'
Then I type $set_cursor on the prompt and the first expansion goes well, but the second just prints
script_name parameter1 /some/path/ parameterN; ^[[10D
Instead of setting the cursor in place.
What is the point i'm missing? I suppose this can be achieved, but I'm misunderstanding the use or having some misconception.
Thanks.
Related
I'm trying to add () around my Python virtual environment name like this:
(my-env) my-user#my-machine:%
and if the env is not set, it will only show:
my-user#my-machine:%
Right now I have:
MYPS1+='($PYENV_VERSION) '
which will show the () if the virtual env is not set:
() my-user#my-machine:%
Is there away I can do something like this:
MYPS1+='($PYENV_VERSION) ' if $PYENV_VERSION exists else ''
So the important thing when setting the prompt like this, is that you (probably) want to reevaluate it every time it prints the prompt. That way if and when the envvar changes, the prompt changes. That's why you have ' characters around what you're adding to the prompt -- it prevents any vars or code in there from being evaluated when you set it. While you could do something like you suggest (with an if in the shell) that would not be reevaluated when the prompt was printed, so could be "stale".
Instead you want to do it all in the variable expansion. sh/bash comes with a variety of ways of expanding variables but the one you want is
${parameter:+word}
Use Alternative Value. If parameter is unset or null, null is substituted; otherwise, the expansion of word is substituted.
That means you want something like
MYPS1+='${PYENV_VERSION:+($PYENV_VERSION) }'
I'm sure I'm missing something stupid. I want to pass a full path variable to a perl script, where I do some work on it and then pass it back. So I have:
echo "Backing up: $f ";
$write_file="$(perl /home/spider/web/foo.com/public_html/gen-path.cgi $f)";
echo "WRITE TO: $write_file \n";
However, this gives me:
Backing up: /home/spider/web/foo.com/public_html/websites-uk/uk/q/u
backup-files-all.sh: line 7: =backup-uk-q-u.tar.gz: command not found
WRITE TO: \n
I can't work out why its not saving the output into $write_file. I must be missing something (bash isn't my prefered language, which is why I'm passing to Perl as I'm a lot more fluent in that :))
Unless your variable write_file already exists, the command $write_file="something" will translate to ="something"(1).
When setting a variable, leave off the $ - you only need it if you want the value of the variable.
In other words, what you need is (note no semicolons needed):
write_file="$(perl /home/spider/web/foo.com/public_html/gen-path.cgi $f)"
(1) It can be even hairier if it is set to something. For example, the code:
write_file=xyzzy
$write_file="something"
will result in something being placed into a variable called xyzzy, not write_file :-)
I have a text file called OPTIONS.txt storing all flags of Makefile:
arg1=foo arg2="-foo -bar"
I want to pass all flags in this file to make. However,
make `cat OPTIONS.txt`
fails with make: invalid option -- 'a'. It seems that shell interprets it as:
make arg1=foo arg2="-foo -bar"
^argv[1] ^argv[2] ^argv[3]
Is there any way to make it interpreted as:
make arg1=foo arg2="-foo -bar"
^argv[1] ^--------argv[2]
Since you control the options file, store the options one per line:
arg1=foo
arg2="-foo -bar"
Then in the shell, you'll read the file into an array, one element per line:
readarray -t opts < OPTIONS.txt
Now you can invoke make and keep the options whole:
make "${opts[#]}"
If you want the shell to interpret quotes after backtick expansion you need to use eval, like this:
eval make `cat OPTIONS.txt`
however just be aware that this evaluates everything, so if you have quoted content outside of the backticks you'll get the same issue:
eval make `cat OPTIONS.txt` arg4="one two"
will give an error. You'd have to double-quote the arg4, something like this:
eval make `cat OPTIONS.txt` arg4='"one two"'
In general it's tricky to do stuff like this from the command line, outside of scripts.
ETA
The real problem here is that we don't have a set of requirements. Why do you want to put these into a file, and what kind of things are you adding; are they only makefile variable assignments, or are there other make options here as well such as -k or similar?
IF the OP controls (can change) the format of the file AND the file contains content only used by make AND the OP doesn't care about the variables being command line assignments vs. regular assignments AND there are only variable assignments and not other options, then they can just (a) put each variable assignment on its own line, (b) remove all quotes, and (c) use include OPTIONS.txt from inside the makefile to "import" them.
I want to create a shell alias which would run
command ew --constantswitch --anotherconstantswitch <name>
Now the value name needs to be extracted from the current path. the current path looks like this
[username#path-to-shell-xxxxxxxx]/path/to/directory/with/name%
How can I create an alias such that when I run aliasX it will
Extract the name from current path (which is last value of the prompt)
Add this path to the command above and execute.
An alias may not be competent for the job, but a function surely do. Try this code:
myfunc() {
command ew --constantswitch --anotherconstantswitch "${PWD##*/}"
}
The trick is ${PWD##*/}. You know the automatic variable $PWD is exactly what you get when you run pwd, as well as Bash's builtin string substitution ${var##pattern} that removes pattern from the left of the variable with maximum match. So ${PWD##*/} removes everything except the name after the last slash, which as you described is what you're looking for.
In practice, a function is more versatile than an alias. If you still need to add extra arguments to the command, append "$#" to the end of the command inside the function, so any argument that you pass to the function will be forwarded to the command.
Since you're not trying to do anything involving arguments, an alias is actually possible:
alias aliasX='echo "${PWD##*/}"'
This will print the current directory name when you use aliasX. Or, using your example:
alias aliasX='command ew --constantswitch --anotherconstantswitch "${PWD##*/}"'
Notice that the alias must be in single quotes or $PWD will expand when you define it instead of when you use it.
For anything slightly more complex, you should use a function instead of an alias, as shown in iBug's answer.
I would like to know if I can substitute a variable twice.
For example:
#global variable
TEST_SERV_EXT=""
#variables become from myconf.sh
TEST_SERV_EXT_FO='foo01'
TEST_SERV_EXT_BR='bar01'
I want dynamically construct those last two and assign them in TEST_SERV_EXT.
I tried something like this ${$TEST_SERV_COMP} but I'm getting "bad substitution" message.
I need something like php's feature "$$" or tcl's subst command.
Regards,
thandem
TEST_SERV_COMP=TEST_SERV_EXT_FO
TEST_SERV_EXT=${!TEST_SERV_COMP}
Look for indirect expansion in the bash manual.