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sh: Various updates to the TOUR document.

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This commit is contained in:
Jilles Tjoelker 2011-05-27 16:00:37 +00:00
parent 715a0dd556
commit 241f15dfaf
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=222362
1 changed files with 8 additions and 29 deletions
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@ -27,10 +27,8 @@ programs is:
mkbuiltins builtins builtins.h builtins.c
mkinit *.c init.c
mknodes nodetypes nodes.h nodes.c
mksignames - signames.h signames.c
mksyntax - syntax.h syntax.c
mktokens - token.h
bltin/mkexpr unary_op binary_op operators.h operators.c
There are undoubtedly too many of these. Mkinit searches all the
C source files for entries looking like:
@ -64,14 +62,6 @@ tion:
Preprocessor #define statements are copied to init.c without any
special action to request this.
INDENTATION: The ash source is indented in multiples of six
spaces. The only study that I have heard of on the subject con-
cluded that the optimal amount to indent is in the range of four
to six spaces. I use six spaces since it is not too big a jump
from the widely used eight spaces. If you really hate six space
indentation, use the adjind (source included) program to change
it to something else.
EXCEPTIONS: Code for dealing with exceptions appears in
exceptions.c. The C language doesn't include exception handling,
so I implement it using setjmp and longjmp. The global variable
@ -115,7 +105,7 @@ repeatedly parses and executes commands.
OPTIONS.C: This file contains the option processing code. It is
called from main to parse the shell arguments when the shell is
invoked, and it also contains the set builtin. The -i and -j op-
invoked, and it also contains the set builtin. The -i and -m op-
tions (the latter turns on job control) require changes in signal
handling. The routines setjobctl (in jobs.c) and setinteractive
(in trap.c) are called to handle changes to these options.
@ -123,10 +113,11 @@ handling. The routines setjobctl (in jobs.c) and setinteractive
PARSING: The parser code is all in parser.c. A recursive des-
cent parser is used. Syntax tables (generated by mksyntax) are
used to classify characters during lexical analysis. There are
three tables: one for normal use, one for use when inside single
quotes, and one for use when inside double quotes. The tables
are machine dependent because they are indexed by character vari-
ables and the range of a char varies from machine to machine.
four tables: one for normal use, one for use when inside single
quotes and dollar single quotes, one for use when inside double
quotes and one for use in arithmetic. The tables are machine
dependent because they are indexed by character variables and
the range of a char varies from machine to machine.
PARSE OUTPUT: The output of the parser consists of a tree of
nodes. The various types of nodes are defined in the file node-
@ -242,12 +233,7 @@ The routine shellexec is the interface to the exec system call.
EXPAND.C: Arguments are processed in three passes. The first
(performed by the routine argstr) performs variable and command
substitution. The second (ifsbreakup) performs word splitting
and the third (expandmeta) performs file name generation. If the
"/u" directory is simulated, then when "/u/username" is replaced
by the user's home directory, the flag "didudir" is set. This
tells the cd command that it should print out the directory name,
just as it would if the "/u" directory were implemented using
symbolic links.
and the third (expandmeta) performs file name generation.
VAR.C: Variables are stored in a hash table. Probably we should
switch to extensible hashing. The variable name is stored in the
@ -292,14 +278,7 @@ when the program is linked into ash. This #define should appear
before bltin.h is included; bltin.h will #undef main if the pro-
gram is to be compiled stand-alone.
CD.C: This file defines the cd and pwd builtins. The pwd com-
mand runs /bin/pwd the first time it is invoked (unless the user
has already done a cd to an absolute pathname), but then
remembers the current directory and updates it when the cd com-
mand is run, so subsequent pwd commands run very fast. The main
complication in the cd command is in the docd command, which
resolves symbolic links into actual names and informs the user
where the user ended up if he crossed a symbolic link.
CD.C: This file defines the cd and pwd builtins.
SIGNALS: Trap.c implements the trap command. The routine set-
signal figures out what action should be taken when a signal is