# Command: extract¶

## COMMAND¶

extract – get specified spines from a Humdrum input

## SYNOPSIS¶

 extract -f field1,field2,...,$-1,$ [inputfile ...] extract -i interp1,interp2,...,interpn [inputfile ...] extract -p spine#n [inputfile ...] extract -t field_trace_file.ftf [inputfile ...]

## DESCRIPTION¶

The extract command allows the user to select one or more spines from a Humdrum input. The command is typically used to extract parts (such as a tuba part) from some multi-part score; however extract can be used to isolate dynamic markings, musical lyrics, or any other stream of information that has been encoded as a separate Humdrum spine.

The extract” command has four distinct modes of operation: (1) field mode (-f), (2) interpretation mode (-i), (3) spine-path mode (-p), and (4) field-trace mode (-t). The simplest mode is field mode; the most general-purpose mode is field-trace mode.

In field mode, the extract” command operates in a manner similar to the UNIX  cut command. The user may specify a given field (data column) or set of fields to be selected from the input stream. For example, the command:

 extract -f 1,3,8

will extract the first, third, and eighth spines from the input stream. In field mode, field specifications may also be made with respect to the right-most field. For example, the expression  “$” refers to the right-most field in the input; the arithmetic expression  “$-1” refers to the right-most field minus one, etc. By way of example, the command:

 extract -f ‘2,4-6,$’ lassus will extract the second, fourth, fifth, sixth, and last (right-most) spines in the file “lassus.” The  extract -f command differs from the UNIX  cut command in that Humdrum global comments are properly preserved in the output. In interpretation mode, the extract command outputs all spines containing the interpretation(s) specified by the user. By way of example, the command:  extract -i ‘**semits,**MIDI’ hildegard will extract all spines in the file hildegard containing **semits or **MIDI data. In spine-path mode, the extract” command follows a given spine starting at the beginning of the file, and traces the course of that spine throughout the input stream. If spine-path changes are encountered in the input (such as spine-exchanges, spine-merges, or spine-splits) the output adapts accordingly. By way of example, if the “third” spine is selected, the output consists of the third spine and follows the path of that spine through the input until it is terminated or the end-of-file is encountered. What begins as the third column, may end up as some other column (or columns) in the input. In the field-trace mode, the extract command accepts a list of spine-column positions over the course of the file. In the field-trace mode, the user provides a file containing a list specifying the precise selection of spines through the file at various line numbers. The first column in this list specifies the line (record) number at which the field selection is defined. The second column lists the spine or spines to be extracted beginning at the specified line. For example, the following field-trace file specifies that the first spine from line 1 should be output; beginning at line 2, spines 3, 4, and 5 should be output; beginning at line 18, spines 1 and 4 should be output, and from line 78 to the end of the input, spine 9 should be output.  1 1 2 3-5 18 1,4 78 9 The field-trace mode allows the user to select virtually any combination of data tokens from the input stream. Note that using the field-trace mode may produce output that no longer conforms to the Humdrum syntax. (See EXAMPLES below.) ## OPTIONS¶ The extract command provides the following options:  -f fieldlist select field mode -h displays a help screen summarizing the command syntax -i interplist select interpretation mode -p spine# select spine-path mode -t fieldtrace file select field-trace mode Options are specified in the command line. A fieldlist consists of any set of integers separated by commas, or a range specification in which the lower and upper values are separated by a dash: e.g.1,4-8,13. With the exception of range specifications, the order of the integers in the list is unimportant, hence 13,1,4-8 is equivalent to 1,4-8,13. The right-field anchor ($) can be used only with the -f option.

An interplist consists of any set of tandem or exclusive interpretations separated by commas, e.g.'**kern,*C:' Option arguments may require the use of quotation marks in order to prevent inadvertent expansion of shell metacharacter (*, ?, etc.).

## EXAMPLES¶

The following examples illustrate how extract may be used.

 extract -f ‘1,3,$’ holst outputs the first, third, and last columns from the file holst.  extract -p 4 mossolov outputs the spine beginning (but not necessarily continuing) in the fourth column of the file mossolov.  extract -t sibelius.fld sibelius outputs the spines specified in the file sibelius.fld for the file sibelius. (See SAMPLE OUTPUTS below.)  extract -i ‘*F:,*f:’ hendrix outputs all spines that contain the tandem interpretations *F: or *f: (i.e. in the keys of F major or F minor). ## SAMPLE OUTPUTS¶ The following examples illustrate the various extract options. Consider the following input file, dubbed input1:  !! extract’ example #1 **ABC **xyz **123 **ABC **foo A x 1 a bar B y 2 b . C z 3 c # *- *- *- *- *- Executing either of the following commands:  extract -f ‘1,3,$-1’ input1 > output

or

 extract -i ‘**ABC,**123’ input1 > output

would produce the following result: 

!! extract’ example #1 **ABC **123 **ABC A 1 a B 2 b C 3 c *- *- *-

Consider next the following sample input – dubbed input2: 

!! extract’ example #2 **ABC **xyz **123 **ABC **foo A x 1 a % * * *^ * * B y 2a 2b b & C z 3a 3b c # * *x *x * * * A 4a xyz 4b d % *- * * * *- * 5a xyz 5b & * *x *x * 6a 6b xyz # *v *v * * 7 xyz % 8 xyz & *- *- *-

Executing the command:

 extract -p 3 input2 > output

would produce the following result: 

!! extract’ example #2 **123 1 *^ 2a 2b 3a 3b *x * 4a 4b * * 5a 5b * *x 6a 6b *v *v 7 8 *-

Notice that this output no longer conforms to the Humdrum syntax. (Output lines 7 and 11 contain only a single exchange-path interpretation.)

### For the example #2’ input file, the field-structure is as follows:¶

 1 1-1 # Line 1 must appear in the file. 4 1-5 # * * *^ * * .... 5 1-6 # Line after path indicator record 7 1-6 # * *x *x * .... 8 1-6 # Line after path indicator record 9 1-6 # *- * * * * .... 10 1-4 # Line after path indicator record 11 1-4 # * *x *x * .... 12 1-4 # Line after path indicator record 13 1-4 # *v *v * * .... 14 1-3 # Line after path indicator record 16 1-3 # *- *- *- ....

(The above file may be generated via the  fields -s command.) On the basis of this information a user might create the following field-trace file, dubbed trace: 

 1 1 4 3 5 3,5 7 2,3 8 3,2 9 1,3 10 4 14 3 15 2 16 1

Executing the following command:

 extract -t trace input2 > output

would produce the following result: 

!! extract’ example #2 **ABC A *^ 2a b 3a c *x *x 4a xyz *- * & * # * % xyz *-

Notice that in this case, data tokens have been selected from a variety of input spines.

## DIAGNOSTICS¶

In field-trace mode, if the specified field-structure does not correspond to the actual input file, then an ERROR message is issued.

## PORTABILITY¶

DOS 2.0 and up, with the MKS Toolkit. OS/2 with the MKS Toolkit. UNIX systems supporting the Korn shell or Bourne shell command interpreters, and revised awk (1985).

## WARNINGS¶

Note that only the field mode (-f) guarantees that the output will conform to the Humdrum syntax.

In interpretation mode, tandem interpretations may be specified in the command invocation, but mutually exclusive tandem interpretations (such as changes of key) will not force the program to stop outputting a specified spine.