(m4.info.gz) M4exit

Info Catalog

(m4.info.gz) Location

(m4.info.gz) Miscellaneous

 
 13.3 Exiting from `m4'
 ======================
 
 If you need to exit from `m4' before the entire input has been read,
 you can use `m4exit':
 
  -- Builtin: m4exit ([CODE = `0'])
      Causes `m4' to exit, with exit status CODE.  If CODE is left out,
      the exit status is zero.  If CODE cannot be parsed, or is outside
      the range of 0 to 255, the exit status is one.  No further input
      is read, and all wrapped and diverted text is discarded.
 
    A common use of this is to abort processing:
 
  -- Composite: fatal_error (MESSAGE)
      Abort processing with an error message and non-zero status.  Prefix
      MESSAGE with details about where the error occurred, and print the
      resulting string to standard error.
 
      define(`fatal_error',
             `errprint(__program__:__file__:__line__`: fatal error: $*
      ')m4exit(`1')')
      =>
      fatal_error(`this is a BAD one, buster')
      error-->m4:stdin:4: fatal error: this is a BAD one, buster
 
    After this macro call, `m4' will exit with exit status 1.  This macro
 is only intended for error exits, since the normal exit procedures are
 not followed, e.g., diverted text is not undiverted, and saved text
 ( M4wrap) is not reread.  (This macro has a subtle bug, when
 invoked from wrapped text.  You should try to see if you can find it and
 correct it.   Answers)
 
      m4wrap(`This text is lost to `m4exit'.')
      =>
      divert(`1') And so is this.
      divert
      =>
      m4exit
 
    Note that it is still possible for the exit status to be different
 than what was requested by `m4exit'.  If `m4' detects some other error,
 such as a write error on standard out, the exit status will be non-zero
 even if `m4exit' requested zero.
 
    If standard input is seekable, then the file will be positioned at
 the next unread character.  If it is a pipe or other non-seekable file,
 then there are no guarantees how much data `m4' might have read into
 buffers, and thus discarded.
 

Info Catalog

(m4.info.gz) Location

(m4.info.gz) Miscellaneous