e45f5509 |
1 | .\" -*-nroff-*- |
2 | .\" |
3 | .\" $Id: sw-env.5,v 1.1 1999/06/04 13:56:18 mdw Exp $ |
4 | .\" |
5 | .\" Manual page for `sw-env' files |
6 | .\" |
7 | .\" (c) 1999 EBI |
8 | .\" |
9 | .\"----- Licensing notice --------------------------------------------------- |
10 | .\" |
11 | .\" This file is part of sw-tools. |
12 | .\" |
13 | .\" sw-tools is free software; you can redistribute it and/or modify |
14 | .\" it under the terms of the GNU General Public License as published by |
15 | .\" the Free Software Foundation; either version 2 of the License, or |
16 | .\" (at your option) any later version. |
17 | .\" |
18 | .\" sw-tools is distributed in the hope that it will be useful, |
19 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of |
20 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
21 | .\" GNU General Public License for more details. |
22 | .\" |
23 | .\" You should have received a copy of the GNU General Public License |
24 | .\" along with sw-tools; if not, write to the Free Software Foundation, |
25 | .\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
26 | .\" |
27 | .\"----- Revision history --------------------------------------------------- |
28 | .\" |
29 | .\" $Log: sw-env.5,v $ |
30 | .\" Revision 1.1 1999/06/04 13:56:18 mdw |
31 | .\" New manual page. |
32 | .\" |
33 | .\" |
34 | .\" --- Useful macro definitions --- |
35 | .\" |
36 | .de VS \" Start a sort-of verbatim block |
37 | .sp 1 |
38 | .in +5n |
39 | .nf |
40 | .ft B |
41 | .. |
42 | .de VE \" Stop a sort-of verbatim block |
43 | .ft R |
44 | .fi |
45 | .in -5n |
46 | .sp 1 |
47 | .. |
48 | .de HP \" Start an indented paragraph with a bold right-aligned label |
49 | .IP |
50 | \fB\h'-\w'\\$1\ 'u'\\$1\ \fP\c |
51 | .. |
52 | .\" |
53 | .\" --- Style hacking --- |
54 | .\" |
55 | .ie \n(.g \{\ |
56 | . fam P |
57 | . ds mw \fR[\f(BImdw\fR] |
58 | .\} |
59 | .el .ds mw \fR[\fBmdw\fR] |
60 | .ie t .ds o \(bu |
61 | .el .ds o o |
62 | .ds sw \fBsw\fP |
63 | .ds se \fBsw\-env\fP |
64 | .\" |
65 | .\" --- Main manual text --- |
66 | .\" |
67 | .TH sw 1 "25 May 1999" "EBI tools" |
68 | .PD 1 |
69 | .\" |
70 | .SH NAME |
71 | sw\-env \- environment variable assignment files for \*(sw. |
72 | .\" |
73 | .SH DESCRIPTION |
74 | A \*(se file is a sequence of statements. The following statements are |
75 | supported: |
76 | .sp 1 |
77 | .in +5n |
78 | .B : |
79 | .I value |
80 | .RB [ ; ] |
81 | .br |
82 | .B include |
83 | .I value |
84 | .RB [ ; ] |
85 | .br |
86 | .B arch |
87 | .I value |
88 | .B { |
89 | .IR statement ... |
90 | .B } |
91 | .RB [ ; ] |
92 | .br |
93 | .RB [ set ] |
94 | .I name |
95 | .RB [ = ] |
96 | .I value |
97 | .RB [ ; ] |
98 | .br |
99 | .B unset |
100 | .I name |
101 | .RB [ ; ] |
102 | .in -5n |
103 | .sp 1 |
104 | Whitespace serves to separate tokens but is otherwise ignored except |
105 | when it occurs quoted within a |
106 | .IR value . |
107 | The file may also contain comments, which begin with a |
108 | .RB ` # ' |
109 | character and extend to the end of the line. The start of a comment |
110 | must appear where a new statement is expected. Apart from its behaviour |
111 | of terminating comments, newlines behave the same way as other |
112 | whitespace characters. Keywords are not reserved words. |
113 | .PP |
114 | A |
115 | .I name |
116 | is a sequence of digits, letters and underscores which does not start |
117 | with a digit. |
118 | .PP |
119 | A |
120 | .I value |
121 | may contain any non-null character, although some characters are special |
122 | and must be quoted. The syntax of |
123 | .IR value s |
124 | is loosely based on the Bourne |
125 | shell, although there are differences and irregularities due to the |
126 | quick and dirty nature of the parser. The various quoting and |
127 | substitution operations are described below. |
128 | .SS "Statements" |
129 | The statements behave as follows: |
130 | .TP |
131 | .B : |
132 | The following |
133 | .I value |
134 | is read and discarded. This is not useless: reading a |
135 | .I value |
136 | may cause variables to be assigned as a result of |
137 | `\c |
138 | .BI ${ name = value }\c |
139 | \&' substitutions. |
140 | .TP |
141 | .B include |
142 | A |
143 | .I value |
144 | is read, and further assignments are read from the file so named, if it |
145 | exists. Conventionally, the last statement in the global \*(se file is |
146 | .VS |
147 | include ".sw-env"; |
148 | .VE |
149 | to read in package-specific settings. |
150 | .TP |
151 | .B arch |
152 | The following |
153 | .I value |
154 | is read. If it matches the name of the host's architecture, then the |
155 | brace-enclosed statements are executed; otherwise they're ignored. It's |
156 | possible, though not useful, to nest |
157 | .B arch |
158 | statements. |
159 | .TP |
160 | .B set |
161 | A |
162 | .I name |
163 | and |
164 | .I value |
165 | are read, optionally separated by an |
166 | .RB ` = ' |
167 | character. The variable named is assigned the value, replacing any |
168 | previously assigned value, if any. The |
169 | .RB ` set ' |
170 | keyword is optional. It's only useful so that you can assign values to |
171 | variables whose names are also statement keywords. |
172 | .TP |
173 | .B unset |
174 | A |
175 | .I name |
176 | is read. Any value assigned to the variable named is discarded, and the |
177 | variable is forgotten. |
178 | .SS "Value syntax" |
179 | The parser usually reads a |
180 | .I value |
181 | a character by character, until it finds a delimiter. Delimiter |
182 | characters are |
183 | .RB ` ( ', |
184 | .RB ` ) ', |
185 | .RB ` { ', |
186 | .RB ` } ', |
187 | and |
188 | .RB ` ; '; |
189 | whitespace also acts as a delimiter. Delimiter characters can only |
190 | appear in a value if quoted. |
191 | .PP |
192 | There are three types of quoting understood by the value reader. A |
193 | backslash |
194 | .RB (` \e ') |
195 | character causes the following character to be stripped of its special |
196 | meaning. Hence |
197 | .RB ` \e\e ' |
198 | inserts a literal backslash. Text between single quotes |
199 | .RB ` \' ... \' ' |
200 | is read |
201 | entirely as-is, including all whitespace, newlines, backslashes, |
202 | everything. To include a single quote in a piece of single-quoted text, |
203 | use the sequence |
204 | .RB ` \'\e\'\' ', |
205 | as in the shell. (This drops out of single-quoting, inserts an escaped |
206 | single quote, and resumes quoting.) Text between double quotes |
207 | .BR """" ... """" |
208 | is partially quoted: delimiters and whitespace are read as normal |
209 | characters, but substitutions using the |
210 | .RB ` $ ' |
211 | and |
212 | .RB ` \` ' |
213 | characters are still made, and the backslash retains its behaviour of |
214 | escaping the following character. |
215 | .PP |
216 | Two sorts of substitutions are available in values: |
217 | .I "variable substitution" |
218 | examines a variable and substitutes some text based on its value, and |
219 | .I "command substitution" |
220 | runs a command and substitutes its output. |
221 | .PP |
222 | The simplest variable substitution takes the form |
223 | .RB ` $\c |
224 | .IR name ': |
225 | this is replaced by the value of the variable called |
226 | .IR name , |
227 | or the empty string if there is no such variable defined. The name may |
228 | be enclosed in braces should it be necessary to clearly disambiguate the |
229 | end of the name. |
230 | .PP |
231 | More complex variable substitutions are permitted: |
232 | .TP |
233 | .BI ${ name \- text } |
234 | Expands to the value of the variable called |
235 | .I name |
236 | if it's defined, or |
237 | .I text |
238 | if not. |
239 | .TP |
240 | .BI ${ name + text } |
241 | Expands to |
242 | .I text |
243 | if there is a variable called |
244 | .I name |
245 | defined, or nothing. |
246 | .TP |
247 | .BI ${ name = text } |
248 | If there is no variable called |
249 | .I name |
250 | then create one with the value |
251 | .IR text ; |
252 | then expands to the variable's value. |
253 | .PP |
254 | In each of the above, prefixing the operator character |
255 | .RB ` \- ', |
256 | .RB ` + ' |
257 | or |
258 | .RB ` = ' |
259 | with a colon |
260 | .RB (` : ') |
261 | changes the variable existence test, such that it will believe that a |
262 | variable whose value is the empty string is not defined. Each |
263 | .I text |
264 | part in the above forms is syntactically a |
265 | .IR value , |
266 | and may itself contain quoting and substitutions. It may also contain |
267 | unescaped whitespace. |
268 | .PP |
269 | There are two forms for command substitution: the backtick form, where a |
270 | command is enclosed in backquotes |
271 | .RB ` \` ... \` '; |
272 | and the parenthesized form |
273 | .RB ` $( ... ) '. |
274 | The only difference between these two forms is syntactic: it's easy to |
275 | make the parenthesized version nest, although that's not actually very |
276 | useful. The text between the backquotes or parentheses is broken into |
277 | words and executed as a command. It is not passed through the shell: |
278 | the author suspects that this would be too confusing. The standard |
279 | output of the command, with trailing newlines (but not internal or |
280 | leading newlines) removed, is the result of the substitution. |
281 | .SH AUTHOR |
282 | The \*(sw program, and this manual, are \*(mw productions, in association |
283 | with the European Bioinformatics Institute. They were written by Mark |
284 | Wooding <mdw@nsict.org>. Go and ask him if you have problems. |