1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
.de URL
\\$2 \(laURL: \\$1 \(ra\\$3
..
.if \n[.g] .mso www.tmac
.TH REDO-IFCHANGE 1
.SH NAME
redo-ifchange \- rebuild target files when source files have changed
.SH SYNOPSIS
.B redo-ifchange
.I target
.RI [ target ]...
.SH DESCRIPTION
.IR redo(1)
is a tool for building files and for rebuilding them if any of their dependencies have changed.
.IR redo-ifchange ,
when invoked from a dofile, adds dependencies of the current
.IR redo(1)
target on all files given as arguments, (re)builds those files if necessary and rebuilds the current target if the files given as arguments have changed since the last build.
.PP
Internally
.I redo-ifchange
uses
.IR stat(1)
and
.IR md5sum(1)
or
.IR openssl(1)
or
.IR md5(1)
to determine if a file is out of date. If the ctime of a file did not change since the last build,
.I redo-ifchange
considers the file up to date. If the checksum of a file did not change,
.I redo-ifchange
updates the stored ctime and considers the file up to date. Otherwise,
.I redo-ifchange
considers the file out of date.
.PP
When
.I redo(1)
is invoked with the
.B -j
or
.B --jobs
option and an integer argument greater than 1,
.I redo-ifchange(1)
can build multiple targets in parallel. The integer argument specifies the maximum number of targets that
.I redo-ifchange(1)
is allowed to build in parallel.
.PP
.I redo-ifchange(1)
processes started as a result of the same
.I redo(1)
invocation share knowledge of a temporary “canary” path.
If any
.I redo-ifchange(1)
process exits with a status code indicating error or receives a
.B SIGINT
signal (interrupt from keyboard), it creates a file at the “canary” path. When
.I redo-ifchange(1)
notices such a “canary” file, it exits as soon as possible with a status code indicating error.
.SH EXAMPLES
.PP
Consider the following four files
.IR all.do ,
.IR b.do ,
.IR c
and
.IR d :
.TP
.I all.do
.br
#!/bin/sh
.br
redo-ifchange b
.TP
.I b.do
.br
#!/bin/sh
.br
redo-ifchange c d
.br
date +%s
.TP
.I c
.br
foo
.TP
.I d
.br
bar
.PP
Invoking
.IR redo(1)
in a directory with these files will build a file named
.I b
containing a timestamp. The next time
.IR redo(1)
is invoked, it will only rebuild
.I b
if the contents of
.IR b ,
.IR c
or
.IR d
have changed since the last build. This can be verified by invoking
.IR redo(1) ,
repeatedly and examining the timestamp in
.IR b ,
after each invocation, then changing the contents of
.IR b ,
.IR c
or
.IR d
and invoking
.IR redo(1)
again.
.SH HISTORY
.I redo-ifchange
was designed by D. J. Bernstein and implemented by Nils Dagsson Moskopp.
.TP
.URL https://cr.yp.to/redo/atomic.html "Rebuilding target files atomically" " by D. J. Bernstein"
.SH AUTHOR
.I redo-ifchange
and this man page were written by Nils Dagsson Moskopp.
.SH COPYRIGHT
Copyright © 2014-2016 Nils Dagsson Moskopp.
License AGPLv3+: GNU Affero GPL version 3 or later <http://www.gnu.org/licenses/agpl-3.0.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
.SH SEE ALSO
.IR redo(1) ,
.IR redo-always(1) ,
.IR redo-dot(1) ,
.IR redo-ifcreate(1) ,
.IR redo-ood(1) ,
.IR redo-sources(1) ,
.IR redo-stamp(1) ,
.IR redo-targets(1) ,
.IR signal(7)
.SH BUGS
.I redo-ifchange
erroneously considers target files always out of date if their name contains a tab or a newline character.
.PP
On a computer with a
.IR stat(1)
implementation that does not accept the
.B -c%Y
option,
.I redo-ifchange
considers target files to be always out of date.
.PP
When building in parallel and sending a
.B SIGINT
signal (interrupt from keyboard) to a
.I redo-ifchange(1)
process, other
.I redo-ifchange(1)
processes started from the same
.I redo(1)
invocation might not immediately notice the existence of the “canary“ file and linger for a short time.
|
