cut: provide original-work help message and option descriptions

src/cut/cut.rs

@@ -405,16 +405,16 @@ fn cut_files(mut filenames: Vec<String>, mode: Mode) -> i32 {
 pub fn uumain(args: Vec<String>) -> i32 {
     let mut opts = getopts::Options::new();
 
-    opts.optopt("b", "bytes", "select only these bytes", "LIST");
+    opts.optopt("b", "bytes", "filter byte columns from the input source", "sequence");
-    opts.optopt("c", "characters", "select only these characters", "LIST");
+    opts.optopt("c", "characters", "alias for character mode", "sequence");
-    opts.optopt("d", "delimiter", "use DELIM instead of TAB for field delimiter", "DELIM");
+    opts.optopt("d", "delimiter", "specify the delimiter character that separates fields in the input source. Defaults to Tab.", "delimiter");
-    opts.optopt("f", "fields", "select only these fields;  also print any line that contains no delimiter character, unless the -s option is specified", "LIST");
+    opts.optopt("f", "fields", "filter field columns from the input source", "sequence");
-    opts.optflag("n", "", "(ignored)");
+    opts.optflag("n", "", "legacy option - has no effect.");
-    opts.optflag("", "complement", "complement the set of selected bytes, characters or fields");
+    opts.optflag("", "complement", "invert the filter - instead of displaying only the filtered columns, display all but those columns");
-    opts.optflag("s", "only-delimited", "do not print lines not containing delimiters");
+    opts.optflag("s", "only-delimited", "in field mode, only print lines which contain the delimiter");
-    opts.optopt("", "output-delimiter", "use STRING as the output delimiter the default is to use the input delimiter", "STRING");
+    opts.optopt("", "output-delimiter", "in field mode, replace the delimiter in output lines with this option's argument", "new delimiter");
-    opts.optflag("", "help", "display this help and exit");
+    opts.optflag("", "help", "print usage information");
-    opts.optflag("", "version", "output version information and exit");
+    opts.optflag("", "version", "print version information");
 
     let matches = match opts.parse(&args[1..]) {
         Ok(m) => m,
@@ -425,24 +425,83 @@ pub fn uumain(args: Vec<String>) -> i32 {
     };
 
     if matches.opt_present("help") {
-        println!("{} {}", NAME, VERSION);
+        print!("
-        println!("");
+ {0} {1}
-        println!("Usage:");
+
-        println!("  {0} OPTION... [FILE]...", NAME);
+ {0} [-d] [-s] [-z] [--output-delimiter] ((-f|-b|-c) {{sequence}}) {{sourcefile}}+
-        println!("");
+
-        println!("{}", opts.usage("Print selected parts of lines from each FILE to standard output."));
+ {2}
-        println!("");
+
-        println!("Use one, and only one of -b, -c or -f.  Each LIST is made up of one");
+ Reference
-        println!("range, or many ranges separated by commas.  Selected input is written");
+
-        println!("in the same order that it is read, and is written exactly once.");
+ Each call must specify a mode (what to use for columns), 
-        println!("Each range is one of:");
+ a sequence (which columns to print), and provide a data source
-        println!("");
+
-        println!("  N     N'th byte, character or field, counted from 1");
+ Specifying a mode
-        println!("  N-    from N'th byte, character or field, to end of line");
+
-        println!("  N-M   from N'th to M'th (included) byte, character or field");
+    Use --bytes (-b) or --characters (-c) to specify byte mode
-        println!("  -M    from first to M'th (included) byte, character or field");
+
-        println!("");
+    Use --fields (-f) to specify field mode, where each line is broken into
-        println!("With no FILE, or when FILE is -, read standard input.");
+    fields identified by a delimiter character. For example for a typical CSV
+    you could use this in combination with setting comma as the delimiter
+
+ Specifying a sequence
+
+    A sequence is a group of 1 or more numbers or inclusive ranges separated
+    by a commas.
+    
+    cut -f 2,5-7 some_file.txt
+    will display the 2nd, 5th, 6th, and 7th field for each source line
+    
+    Ranges can extend to the end of the row by excluding the the second number
+
+    cut -f 3- some_file.txt
+    will display the 3rd field and all fields after for each source line
+    
+    The first number of a range can be excluded, and this is effectively the
+    same as using 1 as the first number: it causes the range to begin at the
+    first column. Ranges can also display a single column
+    
+    cut -f 1,3-5 some_file.txt
+    will display the 1st, 3rd, 4th, and 5th field for each source line
+
+    The --complement option, when used, inverts the effect of the sequence
+    
+    cut --complement -f 4-6 some_file.txt
+    will display the every field but the 4th, 5th, and 6th
+    
+ Specifying a data source
+
+    If no sourcefile arguments are specified, stdin is used as the source of
+    lines to print
+    
+    If sourcefile arguments are specified, stdin is ignored and all files are
+    read in consecutively if a sourcefile is not successfully read, a warning
+    will print to stderr, and the eventual status code will be 1, but cut
+    will continue to read through proceeding sourcefiles
+    
+    To print columns from both STDIN and a file argument, use - (dash) as a 
+    sourcefile argument to represent stdin.
+
+ Field Mode options
+
+    The fields in each line are identified by a delimiter (separator)
+    
+    Set the delimiter
+        Set the delimiter which separates fields in the file using the
+        --delimiter (-d) option. Setting the delimiter is optional.
+        If not set, a default delimiter of Tab will be used.
+    
+    Optionally Filter based on delimiter
+        If the --only-delimited (-s) flag is provided, only lines which 
+        contain the delimiter will be printed
+    
+    Replace the delimiter
+        If the --output-delimiter option is provided, the argument used for
+        it will replace the delimiter character in each line printed. This is
+        useful for transforming tabular data - e.g. to convert a CSV to a 
+        TSV (tab-separated file)
+", NAME, VERSION, opts.usage("Prints specified byte or field columns from each line of stdin or the input files"));
         return 0;
     }