I have a test.zsh script that contains echo $ZSH_VERSION and it outputs nothing. From the command line, echo $ZSH_VERSION prints 5.8. Is there a reason why this variable is null inside a zsh script? I am runing macOS 11.1.
As pointed out in the comments, file name extensions like .zsh mean nothing to Unix shells. What matters when sourcing a script is the shebang on the first line of the script. If you want your script to be interpreted by zsh instead, then you need to put this as the first line of your script:
#!/bin/zsh
Related
I'm confused about this code! Why # cant't play a role that takes the length of a string?
string="abcd"
!echo ${#string}
In fact, the code behind # has become commented and cannot be executed!
Any advice?
This works correctly, but you cannot mix python and bash variables in this way. Try this instead:
!string="abcd" && echo ${#string}
The two statements have to be on the same line because in IPython, each ! statement opens a temporary subshell and variables are not persisted between shells. If you want to use multiline bash programs, you can use the %%bash cell magic instead:
%%bash
string="abcd"
echo ${#string}
I would like to pass the output of my R file to a bash script.
The output of the R script being the title of a video: "Title of Video"
And my bash script being simply:
youtube-dl title_of_video.avi https://www.youtube.com/watch?v=w82a1FTere5o88
Ideally I would like the output of the video being "Title of Video".avi
I know I can use Rscript to launch an R script with a bash command but I don't think Rscript can help me here.
In bash you can call a command and use its output further via the $(my_command) syntax.
Make sure your script only outputs the title.
E.g.
# in getTitle.R
cat('This is my title') # note, print would have resulted in an extra "[1]"
# in your bash script:
youtube-dl $(Rscript getTitle.R) http://blablabla
If you want to pass arguments to your R script as well, do so inside the $() syntax; if you want to pass those arguments to your bash script, and delegate them to the R script to handle them, you can use the special bash variables $1 (denote the 1st argument, etc), or $* to denote all arguments passed to the bash script, e.g.
#!/bin/bash
youtube-dl $(Rscript getTitle.R $1) http://blablablabla
(this assumes that getTitle.R does something to those arguments internally via commandArgs etc to produce the wanted title output)
You can call Rscript in bash script and you might assign the output of the R script to a variable in bash script. Check this question. After that you can execute
youtube-dl $outputFromRScript https://www.youtube.com/watch?v=w82a1FTere5o88
I am trying to use environment variables set by ksh and the expect command in the same script. However, if I try to source both of them, it doesnt work. Is there a way to source ksh and expect in the same script?
Do something like
#!/usr/bin/ksh
. /path/to/ksh_stuff.sh
export FOO=bar
# other ksh stuff
expect <<'END_EXPECT'
source /path/to/expect_stuff.exp
send_user "FOO is $env(FOO)\n"
# other expect stuff
END_EXPECT
Adding quotes around the here-doc terminator (<<'END_EXPECT') means that the entire here-doc is single quoted, so ksh will not attempt any parameter substitutions on it. This is a effective way to isolate the expect script's variables from ksh.
In Korn shell you dot in the other script, example:
. ${other_script}
This will run in the same process as the parent script. The other script can see any variables that are defined in the parent script. If you want to sub-shell (to run an external command), then you will need to export any variables first.
If you want to reference environment variables in your expect script, (those that are exported by a ksh script that runs expect in a subshell) then your expect script needs to reference a global array env . For example if your ksh script exports MYPATH variable then subshells to expect, the expect might reference $env(MYPATH)
Is it possible to tell the SHELL, e.g. bash, to use a specific (bash)rc file using .SHELLFLAGS?
Below you will see two examples. The first shows what I want to do, and the second illustrates one way of achieving the desired result.
The reason for me asking is that I have a bashrc file (from OpenFOAM) defining a bunch of variables and functions that I want to use in various recipes.
Thank you for your time.
example (not working)
file: bashrc:
export HELLOWORLD="Hello World"
file: Makefile:
SHELL=/bin/bash
.SHELLFLAGS=--rcfile bashrc --
test:
#\
echo "$${HELLOWORLD}"
example (working)
file: bashrc:
export HELLOWORLD="Hello World"
file: Makefile:
.ONESHELL:
SHELL=/bin/bash
test: ; source bashrc
#\
echo "$${HELLOWORLD}"
If you read the bash man page related to the --rcfile option you'll find:
--rcfile file
Execute commands from file instead of the system wide initial‐
ization file /etc/bash.bashrc and the standard personal initial‐
ization file ~/.bashrc if the shell is interactive (see INVOCA‐
TION below).
Note particularly that the shell must be interactive for this to have any effect, but a shell that make invokes is of course not interactive.
Second, if you read the GNU make manual on .SHELLFLAGS you'll see that the default value is -c (or -ec in POSIX mode); the -c option allows the shell to read the script to run from the command line, which is how make invokes the shell. This means when you replace .SHELLFLAGS with your own value, you have to include that.
So with your makefile when make runs the shell it will use this command line:
/bin/bash --rcfile bashrc -- 'echo "${HELLOWORLD}"'
which is clearly not going to work. You need to set .SHELLFLAGS like this:
.SHELLFLAGS = --rcfile bashrc -ic --
The -i option forces an interactive shell, and you need the -c option to tell make to run the first non-option argument as a command.
I'd like to put some expressions that write stuff to a file directly into a call to Rscript.exe (without specifying file in Rscript [options] [-e expression] file [args] and thus without an explicit R script that is run).
Everything seems to work except the fact that the desired file is not created. What am I doing wrong?
# Works:
shell("Rscript -e print(Sys.time())")
# Works:
write(Sys.time(), file='c:/temp/systime.txt')
# No error, but no file created:
shell("Rscript -e write(Sys.time(), file='c:/temp/systime.txt')")
Rscript parses its command line using spaces as separators. If your R string contains embedded spaces, you need to wrap it within quotes to make sure it gets sent as a complete unit to the R parser.
You also don't need to use shell unless you specifically need features of cmd.exe.
system("Rscript.exe -e \"write(Sys.time(), file='c:/temp/systime.txt')\"")