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Java Forum / General / March 2008Escape Char on linux Bash Process
Hello, we want to try execute a bash command from java but, I need to insert in command a double quotes example: Process p = rt.exec( "echo \"Te st\" " ); but the bash refuse a " value. I have already test any char I thinked (' '' \ \/ ) Do you any idea to escape a " char? Thank you for any help. >Process p = rt.exec( "echo \"Te st\" " ); exec does not understand bash commands directly. See http://mindprod.com/jgloss/exec.html  SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com > Hello, > [quoted text clipped - 4 lines] > > but the bash refuse a " value. That command runs the "echo" command, not bash! Also you need to pass the arguments to the command differently. Use a shell like bash to use quoting: Process p = rt.exec( new String[]{"bash", "-c", "echo \"hello, world!\""} ); should do it. -Wayne >> we want to try execute a bash command from java but, I need to insert >> in command a double quotes example: [quoted text clipped - 7 lines] > should do it. > -Wayne Echo is also a separate command, but as such it needs no special argument escaping: Process p = rt.exec(new String[]{"echo", "hello, world!"} ); If you use any newer than stone aged java versions (1.5 and up), you can also make it shorter: Process p = rt.exec("echo", "hello, world!"); >>> we want to try execute a bash command from java but, I need to insert >>> in command a double quotes example: [quoted text clipped - 15 lines] > can also make it shorter: > Process p = rt.exec("echo", "hello, world!"); If you don't need to process backslash escapes, quotes, and so on, using echo is easier. However I don't think that your "modern stone aged" version will work, did you try it? javac 1.6.0_05 complained when I tried, and the 1.6 API (javadocs) don't list that as a legal version of Runtime.exec() either. Also, just using echo as the command wouldn't permit parsing of the argument string as the OP apparently wanted. You're right, you don't need to parse "hello, world!" but you would need bash or some shell to parse a more complex string including shell variables, wildcards, etc. Interestingly the bash built-in echo command has different semantics than /bin/echo command. As a matter of portability printf should be used instead anyway: String arg = "Hello, \"World\"!"; Process p = rt.exec( new String[]{"bash", "-c", "printf \"%s\\n\"" + arg} ); However that is uglier. -Wayne >>> we want to try execute a bash command from java but, I need to insert >>> in command a double quotes example: [quoted text clipped - 15 lines] > can also make it shorter: > Process p = rt.exec("echo", "hello, world!"); If you don't need to process backslash escapes, quotes, and so on, using echo is easier. However I don't think that your "modern stone aged" version will work, did you try it? javac 1.6.0_05 complained when I tried, and the 1.6 API (javadocs) don't list that as a legal version of Runtime.exec() either. Also, just using echo as the command wouldn't permit parsing of the argument string as the OP apparently wanted. You're right, you don't need to parse "hello, world!" but you would need bash or some shell to parse a more complex string including shell variables, wildcards, etc. Interestingly the bash built-in echo command has different semantics than /bin/echo command. As a matter of portability printf should be used instead anyway: String arg = "Hello, \"World\"!"; Process p = rt.exec( new String[]{"bash", "-c", "printf \"%s\\n\" " + arg} ); However that is uglier. -Wayne >>> we want to try execute a bash command from java but, I need to insert >>> in command a double quotes example: [quoted text clipped - 15 lines] > can also make it shorter: > Process p = rt.exec("echo", "hello, world!"); If you don't need to process backslash escapes, quotes, and so on, using echo is easier. However I don't think that your "modern stone aged" version will work, did you try it? javac 1.6.0_05 complained when I tried, and the 1.6 API (javadocs) don't list that as a legal version of Runtime.exec() either. Also, just using echo as the command wouldn't permit parsing of the argument string as the OP apparently wanted. You're right, you don't need to parse "hello, world!" but you would need bash or some shell to parse a more complex string including shell variables, wildcards, etc. Interestingly the bash built-in echo command has different semantics than /bin/echo command. As a matter of portability printf should be used instead anyway: Process p = rt.exec( new String[]{"bash", "-c", "printf \"%s\\n\" '" + arg + "'"} ); However that is uglier (took me three tries to get the quoting right). -Wayne >> Echo is also a separate command, but as such it needs no special >> argument escaping: [quoted text clipped - 3 lines] >> can also make it shorter: >> Process p = rt.exec("echo", "hello, world!"); > However I don't think that > your "modern stone aged" version will work, did you try it? > javac 1.6.0_05 complained when I tried, and the 1.6 API (javadocs) > don't list that as a legal version of Runtime.exec() either. Damn, you're right here. Typical case of: posted too fast. I (blindly) assumed that they did it like PrintStream's printf with "..."-ified argument, but obviously they omitted that. And there isn't even any other two(or more)- String version of exec, that could have caused ambiguities. Sorry for confusion. > Process p = rt.exec( new String[]{"bash", "-c", > "printf \"%s\\n\" '" + arg + "'"} ); > However that is uglier (took me three tries to get the quoting right). It's still far away from right. Just think about arg values like: "hello'`rm -rf /`'world" (don't try that at home, folks :-) The single quotes don't make it "secure" - unless you preprocess the string and replace every "'" by this: "'\\''" and even then you need to worry about how many backslashes you really need. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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