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How can I use a regular expression to remove the file extension in zhell?

I am trying to simplify my command line java using this zshell script where $1 holds the file name, in this case Hello.java.
# jcr stands for java compile and run
jcr() {
javac $1 # $1 contains the first argument Hello.java
java Hello # I want to replace Hello with a
# regular expression or similar which extracts Hello
}
I need a good reference or cheat sheet for zshell and zhell regular expressions.

You can use a simple string substitution: ${1//.java} This will remove the last occurence of .java from the parameter $1.

IP as Linux array element throws UnknownHostException but as constant works

I have the following script in the directory /home/test/javacall that parses csv of IP pair , invokes a sh file that calls an executable jar to get output from these IPs.
In the below code ip1=${IPArray[0]} throws UnknownHostException from java.
But If I use the ip directly ip1="10.10.10.10" java code works fine. I did System.out.println from java and I got the same IP displayed in both cases. But in the case of ip1=${IPArray[0]} only, I get the exception.
#!/bin/bash
INPUT="IPPairs.csv"
array=()
while IFS="," read var1 var2 ; do
echo $var1 $var2
pairString="$var1***$var2"
array+=("$pairString")
done < $INPUT
for i in "${array[#]}" ; do
echo $i
IPString=$(echo $i | tr '***' ' ')
read -ra IPArray <<< "$IPString"
ip1=${IPArray[0]}
#ip1="10.10.10.10"
ip2=${IPArray[1]}
source /home/test/javacall/javacmd.sh "$ip1" "/home/test/javacall/out.txt" "show running-config all-properties"
done
Exception:
com.jcraft.jsch.JSchException: java.net.UnknownHostException: 10.10.10.10
at com.jcraft.jsch.Util.createSocket(Util.java:349)
at com.jcraft.jsch.Session.connect(Session.java:215)
at com.jcraft.jsch.Session.connect(Session.java:183)

That string (357\273\277) indicates that your csv file is encoded with a Byte-Order Mark (BOM) at the front of the file. The read command is not interpreting the BOM as having special meaning, just passing on the raw characters, so you see them as part of your output.
Since you didn't indicate how your source file is generated, you may be able to adjust the settings on that end to prevent writing the BOM, which is optional in many cases. Alternatively, you can work around it various ways on the script side. These questions both offer some examples:
How can I remove the BOM from a UTF-8 file?
Cygwin command not found bad characters found in .bashrc 357\273\277
But honestly, if you just follow Charles Duffy's advice and run your file through dos2unix before parsing it, it should clean this up for you automatically. i.e.:
...
array=()
dos2unix $INPUT
while IFS="," read var1 var2 ; do
...
Or, building on Charles' version:
#!/usr/bin/env bash
case $BASH_VERSION in ''|[123].*) echo "ERROR: Bash 4.0+ needed" >&2; exit 1;; esac
INPUT="IPPairs.csv"
declare -A pairs=( )
dos2unix $INPUT
while IFS=$',\r' read -r var1 var2 _ ; do
pairs[$var1]=$var2
done <"$INPUT"
for ip1 in "${!pairs[#]}"; do
ip2=${pairs[$ip1]}
# Using printf %q causes nonprintable characters to be visibly shown
printf 'Processing pair: %q and %q\n' "$ip1" "$ip2" >&2
done
Do note that running dos2unix in your script is not necessarily the best approach, as the file only needs to be converted once. Generally speaking, it shouldn't hurt anything, especially with such a small file. Nonetheless, a better approach would be to run dos2unix as part of whatever process pushes your csv to the server, and keep it out of this script.

System.out.println() only shows visible characters.
If your input file contains DOS newlines, System.out.println() won't show them, but they'll still be present in your command line, and parsed as part of the IP address to connect to, causing an UnknownHostException. Converting it to a UNIX text file, as with dos2unix, or using :set fileformat=unix in vim, is typically the quickest way to fix this.
BTW, if you don't need ordering retained, an associative array is typically a more appropriate data structure to use to store pairs:
#!/usr/bin/env bash
case $BASH_VERSION in ''|[123].*) echo "ERROR: Bash 4.0+ needed" >&2; exit 1;; esac
declare -A pairs=( )
while IFS=$',\r' read -r var1 var2 _ ; do
pairs[$var1]=$var2
done <"$input"
for ip1 in "${!pairs[#]}"; do
ip2=${pairs[$ip1]}
# Using printf %q causes nonprintable characters to be visibly shown
printf 'Processing pair: %q and %q\n' "$ip1" "$ip2" >&2
done
In the above, using IFS=$',\r' prevents LF characters (from the "CRLF" sequence that makes up a DOS newline) from becoming either part of var1 or var2. (Adding an _ placeholder variable to consume any additional content in a given line of the file adds extra insurance towards this point).

How to escape all special characters for ffmpeg drawtext filter in java

Does anyone have a good recipe for escaping all of the special characters (',%,\,:,{,}) from a String in java, that will be used in an ffmpeg drawtext filter chain? Trying to use replaceAll with different combinations of escaping has been an exercise in frustration!
String myTextString = "Bob's special\cool mix:stuff # 40% off";
Runtime.getRuntime().exec(new String[] { "ffmpeg",...., "filter_complex", "drawtext=enable='between(t,0,10)':x=10:y=10:fontfile=Roboto-Black.ttf:text='" + myTextString + "':fontcolor=#a43ddb:fontsize=14", ... });
ffmpeg drawtext filter: https://ffmpeg.org/ffmpeg-filters.html#drawtext-1

Alright...after banging my head against a wall for getting the right escape patterns to satisfy both java and ffmpeg I came up with this:
MyDrawTextString.replaceAll("\\\\", "\\\\\\\\\\\\\\\\").replaceAll("'", "'\\\\\\\\\\\\\''").replaceAll("%", "\\\\\\\\\\\\%").replaceAll(":", "\\\\\\\\\\\\:");
Looks insane, but it works! Note: I had to double my backslashes in my answer here to get this to display correctly too :-P Dang those backslashes.
The key is ffmpeg drawtext needs 3 backslashes to escape (',%,:) and single quotes need to also be wrapped in a second pair of single quotes. Java String needs 2 backslashes to make one and java replaceAll regex needs to have 2 backslashes to make a single one in a string. Therefore you need (2+2)*3 backslashes to escape things in drawtext filter string!

Just put your text into a text file (e.g. myText.txt) and use the textfile option:
-> myText.txt:
This is my text with special characters: ,(,),'
Then instead of using:
ffmpeg -i test.mpg -vf drawtext="This is my text with special characters :,(,),'"
Use the following command:
ffmpeg -i test.mpg -vf drawtext=textfile=textFile.txt

for Python (in Colab)
Hi, I ran into the same issue using Google Colab and Python. For those looking for a solution, this might help.
I execute the ffmpeg commandline as follows:
!ffmpeg ... -filter_complex "$texts" ...
... where texts refers to a string variable containing the mentioned filteres with drawtext option.
For me worked:
texts = ... # init
def normalize_text(t):
return t\
.replace("\\", "\\\\")\
.replace('"', '""')\
.replace("'", "''")\
.replace("%", "\\%")\
.replace(":", "\\:")
texts = normalize_text(texts) #normalize
!ffmpeg ... #execute
As you can see, escaping it once has worked for me. Note: this function might be extended to include certain other characters which will result in an error message being displayed upon execution, something along the lines of "filter could not be parsed" or "no option XXX" and more.
Thanks guys

System.lineSeparator() returns nothing

What should I see when I use the following?
System.out.println("LineSeperator1: "+System.getProperty("line.separator"));
System.out.println("LineSeperator2: "+System.lineSeparator());
I get the following back:
LineSeperator1:
LineSeperator2:
Is it empty? invisible? shouldn there be something like \r or \n?
I use windows 7, eclipse and jdk 1.8.

As you expect, the line separator contains special characters such as '\r' or '\n' that denote the end of a line. However, although they would be written in Java source code with those backslash escape sequences, they do not appear that way when printed. The purpose of a line separator is to separate lines, so, for example, the output of
System.out.println("Hello"+System.lineSeparator()+"World");
is
Hello
World
rather than, say
Hello\nWorld
You can even see this in the output of your code: the output of
System.out.println("LineSeperator1: "+System.getProperty("line.separator"));
had an extra blank line before the output of the next statement, because there was a line separator from System.getProperty("line.separator") and another from the use of println.
If you really want to see what the escaped versions of the line separators look like, you can use escapeJava from Apache Commons. For example:
import org.apache.commons.lang3.StringEscapeUtils;
public class LineSeparators {
public static void main(String[] args) {
String ls1 = StringEscapeUtils.escapeJava(System.getProperty("line.separator"));
System.out.println("LineSeperator1: "+ls1);
String ls2 = StringEscapeUtils.escapeJava(System.lineSeparator());
System.out.println("LineSeperator2: "+ls2);
}
}
On my system, this outputs
LineSeparator1: \n
LineSeparator2: \n
Note that I had to run it in the same folder as the .jar file from the Apache download, compiling and running with these commands
javac -cp commons-lang3-3.4.jar LineSeparators.java
java -cp commons-lang3-3.4.jar:. LineSeparators

Printing something afterwards will show the effect:
System.out.println("a" + System.lineSeparator() + "b");
Gives
a
b

System can not find the specified path while starting a windows service

I have registered a windows service but when trying to start it says,
[SC] StartService FAILED 2:
The system cannot find the file specified.
I checked the regedit where iamgepath is not getting set properly.
path should be D:\abc\Windows.exe but it is D:abcWindows.exe
I am using java to do above things.
Please help.....

Replace slash \ with double slash \\ like below:
"D:\\abc\\Windows.exe"
and it should work

In Java '\' is a character which define escape sequences like \n means new line character, So if you want to use \ as a character in your input string place one more \ before your .
So if you want to write a\b\c write a\b\c
System.out.println("a\b\c"); will print a\b\c