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Top Forums Shell Programming and Scripting Edit first line of a text file Post 302693775 by methyl on Wednesday 29th of August 2012 05:10:01 PM
Old 08-29-2012
As others have pointed out, you cannot edit a file without opening the file. If all you want to do is replace or insert or insert a single line, the simplest and quickest way would be to do it the old way and use ed. If it needs scripting, just put the ed commands in a here document. If you cannot work ed there has to be a problem.


Comments:

Not clear why this is posted in scripting when only two files are mentioned.

I too cannot see why one would want to use awk for basic text editing.

Be wary of the naive sed substitute suggestion because could change lines lines other than the first line. A sed swapping the complete line is safer providing that it is the only line in the file which matches.

Last edited by methyl; 08-29-2012 at 06:15 PM..
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scalac(1)							   USER COMMANDS							 scalac(1)

NAME
scalac - Compiler for the Scala 2 language SYNOPSIS
scalac [ <options> ] <source files> PARAMETERS
<options> Command line options. See OPTIONS below. <source files> One or more source files to be compiled (such as MyClass.scala). OPTIONS
The compiler has a set of standard options that are supported on the current development environment and will be supported in future releases. An additional set of non-standard options are specific to the current virtual machine implementation and are subject to change in the future. Non-standard options begin with -X. Standard Options -g:{none,source,line,vars,notc} "none" generates no debugging info, "source" generates only the source file attribute, "line" generates source and line number information, "vars" generates source, line number and local variable information, "notc" generates all of the above and will not perform tail call optimization. -nowarn Generate no warnings -verbose Output messages about what the compiler is doing -deprecation Indicate whether source should be compiled with deprecation information; defaults to off (accepted values are: on, off, yes and no) Available since Scala version 2.2.1 -unchecked Enable detailed unchecked warnings Non variable type-arguments in type patterns are unchecked since they are eliminated by erasure Available since Scala version 2.3.0 -classpath <path> Specify where to find user class files (on Unix-based systems a colon-separated list of paths, on Windows-based systems, a semi- colon-separate list of paths). This does not override the built-in ("boot") search path. The default class path is the current directory. Setting the CLASSPATH variable or using the -classpath command-line option over- rides that default, so if you want to include the current directory in the search path, you must include "." in the new settings. -sourcepath <path> Specify where to find input source files. -bootclasspath <path> Override location of bootstrap class files (where to find the standard built-in classes, such as "scala.List"). -extdirs <dirs> Override location of installed extensions. -d <directory> Specify where to place generated class files. -encoding <encoding> Specify character encoding used by source files. The default value is platform-specific (Linux: "UTF8", Windows: "Cp1252"). Executing the following code in the Scala interpreter will return the default value on your system: scala> new java.io.InputStreamReader(System.in).getEncoding -target: <target> Specify which backend to use (jvm-1.5,msil). The default value is "jvm-1.5" (was "jvm-1.4" up to Scala version 2.6.1). -print Print program with all Scala-specific features removed -optimise Generates faster bytecode by applying optimisations to the program -explaintypes Explain type errors in more detail. -uniqid Print identifiers with unique names (debugging option). -version Print product version and exit. -help Print a synopsis of standard options. Advanced Options -Xassem <file> Name of the output assembly (only relevant with -target:msil) -Xassem-path <path> List of assemblies referenced by the program (only relevant with -target:msil) -Xcheck-null Emit warning on selection of nullable reference -Xdisable-assertions Generate no assertions and assumptions -Xexperimental enable experimental extensions -Xno-uescape Disable handling of u unicode escapes -Xplug-types Parse but ignore annotations in more locations -Xplugin: <file> Load a plugin from a file -Xplugin-disable: <plugin> Disable a plugin -Xplugin-list Print a synopsis of loaded plugins -Xplugin-opt: <plugin:opt> Pass an option to a plugin -Xplugin-require: <plugin> Abort unless a plugin is available -Xprint: <phases> Print out program after <phases> (see below). -Xprint-pos Print tree positions (as offsets) -Xprint-types Print tree types (debugging option). -Xprompt Display a prompt after each error (debugging option). -Xresident Compiler stays resident, files to compile are read from standard input. -Xshow-class <class> Show class info. -Xshow-object <object> Show object info. -Xshow-phases Print a synopsis of compiler phases. -Xsource-reader <classname> Specify a custom method for reading source files. -Xscript <object> Compile as a script, wrapping the code into object.main(). Compilation Phases initial initializing compiler parse parse source files namer create symbols analyze name and type analysis refcheck reference checking uncurry uncurry function types and applications lambdalift lambda lifter typesasvalues represent types as values addaccessors add accessors for constructor arguments explicitouterclasses make links from inner classes to enclosing one explicit addconstructors add explicit constructor for each class tailcall add tail-calls wholeprog perform whole program analysis addinterfaces add one interface per class expandmixins expand mixins by code copying boxing makes boxing explicit erasure type eraser icode generate icode codegen enable code generation terminal compilation terminated all matches all phases ENVIRONMENT
JAVACMD Specify the java command to be used for running the Scala code. Arguments may be specified as part of the environment variable; spaces, quotation marks, etc., will be passed directly to the shell for expansion. JAVA_HOME Specify JDK/JRE home directory. This directory is used to locate the java command unless JAVACMD variable set. JAVA_OPTS Specify the options to be passed to the java command defined by JAVACMD. With Java 1.5 (or newer) one may for example configure the memory usage of the JVM as follows: JAVA_OPTS="-Xmx512M -Xms16M -Xss16M" With GNU Java one may configure the memory usage of the GIJ as follows: JAVA_OPTS="--mx512m --ms16m" EXAMPLES
Compile a Scala program to the current directory scalac HelloWorld Compile a Scala program to the destination directory classes scalac -d classes HelloWorld.scala Compile a Scala program using a user-defined java command env JAVACMD=/usr/local/bin/cacao scalac -d classes HelloWorld.scala Compile all Scala files found in the source directory src to the destination directory classes scalac -d classes src/*.scala EXIT STATUS
scalac returns a zero exist status if it succeeds to compile the specified input files. Non zero is returned in case of failure. AUTHOR
Written by Martin Odersky and other members of the Scala team. REPORTING BUGS
Report bugs to http://lampsvn.epfl.ch/trac/scala. COPYRIGHT
This is open-source software, available to you under a BSD-like license. See accomponying "copyright" or "LICENSE" file for copying condi- tions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. SEE ALSO
fsc(1), sbaz(1), scala(1), scaladoc(1), scalap(1) version 0.4 April 18, 2007 scalac(1)
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