I am trying to read the filename by the command line,
This is command that our professor wants us to type:
java MultiBinaryClient xxxxxx.edu 6001 < files.txt
I was trying to use args[3] to get the file name, but args only contains "xxxxxx.edu" and "6001". why not "<" and "files.txt" in the args[]? Can anyone help me out?
BTW, I am using MAC terminal to test my code, I believe my professor uses win CMD, will it make differences?
Thank you!
Let's see what each fragment means. This is how we execute a Java class containing a main method:
java MultiBinaryClient
The only command-line arguments that are being passed to your program are these ones:
xxxxxx.edu 6001
And this snippet is not part of the expected arguments to the Java program:
< files.txt
It's just Unix shell syntax to specify that the contents of files.txt must be read into your program via the standard input.
I know it's an old question, but I've had this problem recently. Here's what I've done to handle it:
Well, as the others said, the "<" redirects the file contents to stdin. If you want to use the file contents as program arguments, you can use xargs:
xargs -a FILE java JAVA_ARGS
or, more specifically:
xargs -a FILE java -cp CLASSPATH CLASS_WITH_MAIN_METHOD
< is a redirection. The file will be streaming over stdin.
You should escape the '<'
java MultiBinaryClient xxxxxx.edu 6001 \< files.txt
I am making an NW.js app on macOS, and want to run the app in dev mode
by double-clicking on an icon.
In the first step, I'm trying to make my shell script work.
Using VS Code on Windows (I wanted to gain time), I have created a run-nw file at the root of my project, containing this:
#!/bin/bash
cd "src"
npm install
cd ..
./tools/nwjs-sdk-v0.17.3-osx-x64/nwjs.app/Contents/MacOS/nwjs "src" &
but I get this output:
$ sh ./run-nw
: command not found
: No such file or directory
: command not found
: No such file or directory
Usage: npm <command>
where <command> is one of: (snip commands list)
(snip npm help)
npm#3.10.3 /usr/local/lib/node_modules/npm
: command not found
: No such file or directory
: command not found
Some things I don't understand.
It seems that it takes empty lines as commands.
In my editor (VS Code) I have tried to replace \r\n with \n
(in case the \r creates problems) but it changes nothing.
It seems that it doesn't find the folders
(with or without the dirname instruction),
or maybe it doesn't know about the cd command ?
It seems that it doesn't understand the install argument to npm.
The part that really weirds me out, is that it still runs the app
(if I did an npm install manually)...
Not able to make it work properly, and suspecting something weird with
the file itself, I created a new one directly on the Mac, using vim this time.
I entered the exact same instructions, and... now it works without any
issues.
A diff on the two files reveals exactly zero difference.
What can be the difference? What can make the first script not work? How can I find out?
Update
Following the accepted answer's recommendations, after the wrong line
endings came back, I checked multiple things.
It turns out that since I copied my ~/.gitconfig from my Windows
machine, I had autocrlf=true, so every time I modified the bash
file under Windows, it re-set the line endings to \r\n.
So, in addition to running dos2unix (which you will have to
install using Homebrew on a Mac), if you're using Git, check your
.gitconfig file.
Yes. Bash scripts are sensitive to line-endings, both in the script itself and in data it processes. They should have Unix-style line-endings, i.e., each line is terminated with a Line Feed character (decimal 10, hex 0A in ASCII).
DOS/Windows line endings in the script
With Windows or DOS-style line endings , each line is terminated with a Carriage Return followed by a Line Feed character. You can see this otherwise invisible character in the output of cat -v yourfile:
$ cat -v yourfile
#!/bin/bash^M
^M
cd "src"^M
npm install^M
^M
cd ..^M
./tools/nwjs-sdk-v0.17.3-osx-x64/nwjs.app/Contents/MacOS/nwjs "src" &^M
In this case, the carriage return (^M in caret notation or \r in C escape notation) is not treated as whitespace. Bash interprets the first line after the shebang (consisting of a single carriage return character) as the name of a command/program to run.
Since there is no command named ^M, it prints : command not found
Since there is no directory named "src"^M (or src^M), it prints : No such file or directory
It passes install^M instead of install as an argument to npm which causes npm to complain.
DOS/Windows line endings in input data
Like above, if you have an input file with carriage returns:
hello^M
world^M
then it will look completely normal in editors and when writing it to screen, but tools may produce strange results. For example, grep will fail to find lines that are obviously there:
$ grep 'hello$' file.txt || grep -x "hello" file.txt
(no match because the line actually ends in ^M)
Appended text will instead overwrite the line because the carriage returns moves the cursor to the start of the line:
$ sed -e 's/$/!/' file.txt
!ello
!orld
String comparison will seem to fail, even though strings appear to be the same when writing to screen:
$ a="hello"; read b < file.txt
$ if [[ "$a" = "$b" ]]
then echo "Variables are equal."
else echo "Sorry, $a is not equal to $b"
fi
Sorry, hello is not equal to hello
Solutions
The solution is to convert the file to use Unix-style line endings. There are a number of ways this can be accomplished:
This can be done using the dos2unix program:
dos2unix filename
Open the file in a capable text editor (Sublime, Notepad++, not Notepad) and configure it to save files with Unix line endings, e.g., with Vim, run the following command before (re)saving:
:set fileformat=unix
If you have a version of the sed utility that supports the -i or --in-place option, e.g., GNU sed, you could run the following command to strip trailing carriage returns:
sed -i 's/\r$//' filename
With other versions of sed, you could use output redirection to write to a new file. Be sure to use a different filename for the redirection target (it can be renamed later).
sed 's/\r$//' filename > filename.unix
Similarly, the tr translation filter can be used to delete unwanted characters from its input:
tr -d '\r' <filename >filename.unix
Cygwin Bash
With the Bash port for Cygwin, there’s a custom igncr option that can be set to ignore the Carriage Return in line endings (presumably because many of its users use native Windows programs to edit their text files).
This can be enabled for the current shell by running set -o igncr.
Setting this option applies only to the current shell process so it can be useful when sourcing files with extraneous carriage returns. If you regularly encounter shell scripts with DOS line endings and want this option to be set permanently, you could set an environment variable called SHELLOPTS (all capital letters) to include igncr. This environment variable is used by Bash to set shell options when it starts (before reading any startup files).
Useful utilities
The file utility is useful for quickly seeing which line endings are used in a text file. Here’s what it prints for for each file type:
Unix line endings: Bourne-Again shell script, ASCII text executable
Mac line endings: Bourne-Again shell script, ASCII text executable, with CR line terminators
DOS line endings: Bourne-Again shell script, ASCII text executable, with CRLF line terminators
The GNU version of the cat utility has a -v, --show-nonprinting option that displays non-printing characters.
The dos2unix utility is specifically written for converting text files between Unix, Mac and DOS line endings.
Useful links
Wikipedia has an excellent article covering the many different ways of marking the end of a line of text, the history of such encodings and how newlines are treated in different operating systems, programming languages and Internet protocols (e.g., FTP).
Files with classic Mac OS line endings
With Classic Mac OS (pre-OS X), each line was terminated with a Carriage Return (decimal 13, hex 0D in ASCII). If a script file was saved with such line endings, Bash would only see one long line like so:
#!/bin/bash^M^Mcd "src"^Mnpm install^M^Mcd ..^M./tools/nwjs-sdk-v0.17.3-osx-x64/nwjs.app/Contents/MacOS/nwjs "src" &^M
Since this single long line begins with an octothorpe (#), Bash treats the line (and the whole file) as a single comment.
Note: In 2001, Apple launched Mac OS X which was based on the BSD-derived NeXTSTEP operating system. As a result, OS X also uses Unix-style LF-only line endings and since then, text files terminated with a CR have become extremely rare. Nevertheless, I think it’s worthwhile to show how Bash would attempt to interpret such files.
On JetBrains products (PyCharm, PHPStorm, IDEA, etc.), you'll need to click on CRLF/LF to toggle between the two types of line separators (\r\n and \n).
I was trying to startup my docker container from Windows and got this:
Bash script and /bin/bash^M: bad interpreter: No such file or directory
I was using git bash and the problem was about the git config, then I just did the steps below and it worked. It will configure Git to not convert line endings on checkout:
git config --global core.autocrlf input
delete your local repository
clone it again.
Many thanks to Jason Harmon in this link:
https://forums.docker.com/t/error-while-running-docker-code-in-powershell/34059/6
Before that, I tried this, that didn't works:
dos2unix scriptname.sh
sed -i -e 's/\r$//' scriptname.sh
sed -i -e 's/^M$//' scriptname.sh
If you're using the read command to read from a file (or pipe) that is (or might be) in DOS/Windows format, you can take advantage of the fact that read will trim whitespace from the beginning and ends of lines. If you tell it that carriage returns are whitespace (by adding them to the IFS variable), it'll trim them from the ends of lines.
In bash (or zsh or ksh), that means you'd replace this standard idiom:
IFS= read -r somevar # This will not trim CR
with this:
IFS=$'\r' read -r somevar # This *will* trim CR
(Note: the -r option isn't related to this, it's just usually a good idea to avoid mangling backslashes.)
If you're not using the IFS= prefix (e.g. because you want to split the data into fields), then you'd replace this:
read -r field1 field2 ... # This will not trim CR
with this:
IFS=$' \t\n\r' read -r field1 field2 ... # This *will* trim CR
If you're using a shell that doesn't support the $'...' quoting mode (e.g. dash, the default /bin/sh on some Linux distros), or your script even might be run with such a shell, then you need to get a little more complex:
cr="$(printf '\r')"
IFS="$cr" read -r somevar # Read trimming *only* CR
IFS="$IFS$cr" read -r field1 field2 ... # Read trimming CR and whitespace, and splitting fields
Note that normally, when you change IFS, you should put it back to normal as soon as possible to avoid weird side effects; but in all these cases, it's a prefix to the read command, so it only affects that one command and doesn't have to be reset afterward.
Coming from a duplicate, if the problem is that you have files whose names contain ^M at the end, you can rename them with
for f in *$'\r'; do
mv "$f" "${f%$'\r'}"
done
You properly want to fix whatever caused these files to have broken names in the first place (probably a script which created them should be dos2unixed and then rerun?) but sometimes this is not feasible.
The $'\r' syntax is Bash-specific; if you have a different shell, maybe you need to use some other notation. Perhaps see also Difference between sh and bash
Since VS Code is being used, we can see CRLF or LF in the bottom right depending on what's being used and if we click on it we can change between them (LF is being used in below example):
We can also use the "Change End of Line Sequence" command from the command pallet. Whatever's easier to remember since they're functionally the same.
One more way to get rid of the unwanted CR ('\r') character is to run the tr command, for example:
$ tr -d '\r' < dosScript.py > nixScript.py
I ran into this issue when I use git with WSL.
git has a feature where it changes the line-ending of files according to the OS you are using, on Windows it make sure the line endings are \r\n which is not compatible with Linux which uses only \n.
You can resolve this problem by adding a file name .gitattributes to your git root directory and add lines as following:
config/* text eol=lf
run.sh text eol=lf
In this example all files inside config directory will have only line-feed line ending and run.sh file as well.
For Notepad++ users, this can be solved by:
The simplest way on MAC / Linux - create a file using 'touch' command, open this file with VI or VIM editor, paste your code and save. This would automatically remove the windows characters.
If you are using a text editor like BBEdit you can do it at the status bar. There is a selection where you can switch.
For IntelliJ users, here is the solution for writing Linux script.
Use LF - Unix and masOS (\n)
Scripts may call each other.
An even better magic solution is to convert all scripts in the folder/subfolders:
find . -name "*.sh" -exec sed -i -e 's/\r$//' {} +
You can use dos2unix too but many servers do not have it installed by default.
For the sake of completeness, I'll point out another solution which can solve this problem permanently without the need to run dos2unix all the time:
sudo ln -s /bin/bash `printf 'bash\r'`
im still relatively new to java but i have experienve in scripting like DOS, Windows and Bash. today i would like to EASILY copy recursively the content of an directory (files and directories) from a sourceDir to a destinationDir from my Java CLI App.
i searched the net up and down and found PLENTY of "solutions" to this using Oracles and/or Apaches FileUtils etc. But they all require sort of "reinventing the wheel" and are 20+ Lines of code, handling each and every file and dir separately with great afford for something that on the command line shell is done by a SINGLE LINE.
For both on Windows and linux its usually no more than a simple...
cp -a "$sourceDir"/* "$targetDir" # on linux
or
xcopy /s /e %srcdir%\* %trgtdir% # on windows
Yet I was unable to find a prepared library or tool for java that does just that like xcopy/robocopy or cp on bash without adding my a whole new "copy" Class to my app :/ .
Is there a good reason why i should "re-invent the wheel" and no just do some sort of "external shell execution" to call one of those command line tools to have the job done within 2-3 Lines of Code?
Thanks for any Advice and Explanation.
Axel
Apache Commons I/O has a method that does this, you need to use the three-argument version of FileUtils.copyDirectory rather than the two-argument version (which copies the directory itself rather than its contents):
public static void copyDirectory(File srcDir, File destDir, boolean preserveFileDate)
throws IOException
This method copies the contents of the specified source directory to within the specified destination directory.
Here is a one statement Java solution:
Runtime.exec(new String[] {"sh", "-c",
"cp -a \"" + src + ""/* \"" + target + "\""});
Obviously not portable, but there is no reinvention of wheels here.
The trick is to let the shell handle the wildcard expansion for you.
I searched the net up and down and found PLENTY of "solutions" to this using Oracles and/or Apaches FileUtils etc. handling each and every file and dir separately with great afford for something that on the command line shell is done by a SINGLE LINE.
My initial thought is...
...........................................
Why you say ApacheCommons.FileUtils is 20+ lines of code??
copyDirectoryToDirectory(File srcDir, File destDir) API says :
Copies a directory to within another directory preserving the file dates.
This method copies the source directory and all its contents to a directory of the same name in the specified destination directory.
FileUtils.copyDirectoryToDirectory(new File(folder_source), new File(folder_destiny));
But they all require sort of "reinventing the wheel" and are 20+ Lines of code
Did you check how long is cp command source code?
Here it is: cp.c from www.gnu.org there are more than 1000 lines of code.
I have problem with this annoying ^M, while exporting some data, writing it to a CSV file to be downloaded. I did some research and found out that if the file you are reading comes from a Windows system this issue happens (Windows uses CR (i.e. ^M)/LF pair to indicate the end of a line, while UNIX uses only a LF).
Now can anyone offer me a solution to overcome this problem (like eliminating or replacing ^M ) before putting it to the writer (writer.write(columnToBeInserted);)
You could use unix2dos and dos2unix to convert UNIX and Windows files respectively. Both are available on *nix and Windows platforms. Read more.
Links for Windows
Dos2Unix
Unix2Dos
Also see How to convert files from Dos to Unix in java
As you read each line do
line.replaceAll("\\p{Cntrl}", "");
Or use a tool to do it for you
in linux/unix environment there is a utilities called dos2unix and unix2dos which converts the files from windows to linux format and vise versa .
on windows check this link and download the utility whch will convert from windows to linux format http://www.sg-chem.net/u2win/
is the following command working under Unix&Linux?
ProcessBuilder prcbdoc = new ProcessBuilder("cmd","/C","start", "Documentation.doc");
prcbdoc.directory(new File(currentDir+"/docs/"));
prcbdoc.start();
I'm not sure because of the "cmd" "/c"
€:
What would be an Linux CentOS equivalent command?
No, it doesn't work. From Java documentation:
a command, a list of strings which signifies the external program file to be invoked and its arguments, if any. Which string lists represent a valid operating system command is system-dependent. For example, it is common for each conceptual argument to be an element in this list, but there are operating systems where programs are expected to tokenize command line strings themselves - on such a system a Java implementation might require commands to contain exactly two elements.
To open a document in a portable manner using AWT:
if (Desktop.isDesktopSupported())
Desktop.getDesktop().open(documentPath);
No, this would not work on Linux (or any other Unix, or on the Mac) due to the "cmd /c" and the "start". On the Mac, you'd say "open Documentation.doc".The various Linux desktops have their own versions of the start/open command: gnome-open for the Gnome desktop, and the FreeDesktop semi-standard xdg-open are some possibilities.
No. cmd and /c are relevant only for windows.