r0mk: переводы

→@A HEAD = Major Heading

→to a similar line for Ventura Publisher:

→.Ah "Major Heading"

→Another example comes from the conversion of a file for troff to an ASCII input format for Ventura Publisher. It converts the following line for troff:

→Column3Column4

→Column1Column2

→Note that no spaces are permitted after the backslash. This script produces the following result:

→/2

→s//\

→We can do a variation on the previous example to replace the second tab on each line with a newline.

→The replacement metacharacters are backslash (\), ampersand (&), and \n. The backslash is generally used to escape the other metacharacters but it is also used to include a newline in a replacement string.

→5.3.1 Replacement Metacharacters

→Note that without the numeric flag, the substitute command would replace only the first tab. (Therefore "1" can be considered the default numeric flag.)

→Column1Column2>Column3Column4

→the output produced by running the script on this file will be:

→Column1Column2Column3Column4

→"" represents an actual tab character, which is otherwise invisible on the screen. If the input is a one-line file such as the following:

→s//>/2

→The numeric flag can be used in the rare instances where the regular expression repeats itself on a line and the replacement must be made for only one of those occurrences by position. For instance, a line, perhaps containing tbl input, might contain multiple tabs. Let's say that there are three tabs per line, and you'd like to replace the second tab with ">". The following substitute command would do it:

→Flags can be used in combination where it makes sense. For instance, gp makes the substitution globally on the line and prints the line. The global flag is by far the most commonly used. Without it, the replacement is made only for the first occurrence on the line. The print flag and the write flag both provide the same functionality as the print and write commands (which are discussed later in this chapter) with one important difference. These actions are contingent upon a successful substitution occurring. In other words, if the replacement is made, the line is printed or written to file. Because the default action is to pass through all lines, regardless of whether any action is taken, the print and write flags are typically used when the default output is suppressed (the -n option). In addition, if a script contains multiple substitute commands that match the same line, multiple copies of that line will be printed or written to file.