I'm learning the power of Vagrant, and I have stumbled upon this problem. I am trying to create a text named foo.txt with the text "foo" inside of it.
What I type into the terminal is this:
user#User-MBP data % "foo" > foo.txt
Terminal says:
zsh: command not found: foo
Has anyone encountered this? Thank you in advance for your help!
You can't just throw a string at the file like that. You need to use a program like echo to throw it for you.
echo "foo" > foo.txt
To be a little more clear about why, run man echo.
The echo program "writes arguments to the standard output". Whatever argument you give it (i.e. "foo") it will write to standard output.
You follow that with the > operator which "redirects standard output". Read about that here.
You then specify a file to "catch" the redirected standard output (i.e. foo.txt) which you already did just fine.
Related
I'm using luac -p file.lua to parse files to check for syntax errors. Is it possible to do something like this:
luac -p | [a bunch of text]
Someone mentioned something about 'piping' but I couldn't figure out how that would help.
What I'm wanting to do is take text from a program I am writing and put all that text into the compiler with -p so it just parses the text. Basically I want to check syntax of my program's textarea without having to write it to a file first.
In bash you can do
luac -p - << EOF
Then type your text. To indicate end, just type
EOF
on new line and press enter.
I am basically looking for a way to do this
list=$(command)
while read -r arg
do
...
done <<< "$list"
Using sh intead of bash. The code as it is doesn't run because of the last line:
syntax error: unexpected redirection
Any fixes?
Edit: I need to edit variables and access them outside the loop, so using | is not acceptable (as it creates a sub-shell with independent scope)
Edit 2: This question is NOT similar to Why does my Bash counter reset after while loop as I am not using | (as I just noticed in the last edit). I am asking for another way of achiving it. (The answers to the linked question only explain why the problem happens but do not provide any solutions that work with sh (no bash).
There's no purely syntactic way to do this in POSIX sh. You'll need to use either a temporary file for the output of the command, or a named pipe.
mkfifo output
command > output &
while read -r arg; do
...
done < output
rm output
Any reason you can't do this? Should work .. unless you are assigning any variables inside the loop that you want visible when it's done.
command |
while read -r arg
do
...
done
I'm trying to replace the word in shell script with sed -e command but its not replacing , please help on that, i have tried the below
we have separate file in /data/docs/config.log, in that file there is a word ?account for example ,
username acc, passsword acc, ?account.name
this ?account word needs to be replaced with word 'GLOBAL' using sed -e command ,
reacc = GLOBAL
sed -e "s/?account/$reacc/g" /data/docs/config.log > /data/docs/newconfig.log
but here the file newconfig.log has created with 0 size , no output written to the file , its not replacing its an empty file,
the output should be username acc, passsword acc, GLOBAL.name in newconfig.log
Being the only person who can reproduce the problem, you are pretty much on your own. There are plenty of things you can do to analyze the problem, though.
Double-check the shell. Don't have blind faith in #!/bin/sh. In cygwin for example, /bin/sh is an alias for bash. Verify with: echo $SHELL
Check permissions and file system. Do you have rights to write to the output file? Is the disk full? Does cat /data/docs/config.log > /data/docs/newconfig.log work? Test again in a different folder.
Double-check the output file. Is it really empty, or is the file system just slow with updating the file size? Is sed really finished? Test without output redirection; see if the output is dumped to stdout.
Test with a small file; one or two lines is enough.
If even that does not work, then test sed itself. Who knows, maybe you have a weird alias that hides the real sed. The most trivial filter is sed -e '', which should simply echo every line you type (just like cat without parameters). Does that work? Then try some simple patterns.
Systematically iterate between test cases that succeed and test case that fail, until you have found the breaking point. Doing so, you should be able to find the cause. Sorry, that's all I can do for you right now.
Remove spaces around =. Try after making
reacc=GLOBAL
In bash shell scripting, I would typically run :> file to empty a file.
Now using fish, things are slightly different and the above command doesn't work.
What is fish equivalent?
Although it's not as short as :, true is a command that will work everywhere and produces no output:
true > file
Probably the easiest way that will be work in both Fish and Bash is to do echo "" > file
EDIT: Commenter was absolutely right echo "" > file produces a file with a newline, the correct command I was thinking of to create an empty file is cat /dev/null > file.
There is, and always was the magic method called touch which set change time to actual or create non-existent file. For compatiblity I suggest you to use this way in all scripts that you write (even if you write bash code).
It seems to me that there are two ways to run Matlab in batch mode:
the first one:
unset DISPLAY
matlab > matlab.out 2>&1 << EOF
plot(1:10)
print file
exit
EOF
The second one uses option "-r MATLAB_command":
matlab -nojvm -nosplash -r MyCommand
Are these two equivalent?
What does "<< EOF" and the last "EOF" mean in the first method?
Thanks and regards!
The first method simply redirects the standard output > matlab.out and the standard error 2>&1 to the file matlab.out.
Then it uses the heredoc way of passing input to MATLAB (this is not specific to MATLAB, it is a method of passing multiple lines as input to command line programs in general).
The syntax is << followed by an unique identifier, then your text, finally the unique id to finish.
You can try this on the shell:
cat << END
some
text
multiple lines
END
The second method of using the -r option starts MATLAB and execute the statement passed immediately. It could be some commands or the name of a script or function found on the path.
It is equivalent to doing something like:
python -c "print 'hello world'"
Refer to this page for a list of the other start options.