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authorLudovic Courtès <ludo@gnu.org>2016-09-09 22:46:36 +0200
committerLudovic Courtès <ludo@gnu.org>2016-09-09 23:54:43 +0200
commita9e5e92f940381e3a4ee828c6d8ff22a73067e17 (patch)
tree4d50f44926d0c6a41550014d0ecc5e7deb9a0839 /doc
parentebdfd776f4504c456d383ee8afa59fc6fdfc6756 (diff)
downloadguix-a9e5e92f940381e3a4ee828c6d8ff22a73067e17.tar
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gexp: Add 'file-append'.
* guix/gexp.scm (<file-append>): New record type. (file-append): New procedure. (file-append-compiler): New gexp compiler. * tests/gexp.scm ("file-append", "file-append, output") ("file-append, nested", "gexp->file + file-append"): New tests. * doc/guix.texi (G-Expressions): Use it in 'nscd' and 'list-files' examples. Document 'file-append'.
Diffstat (limited to 'doc')
-rw-r--r--doc/guix.texi35
1 files changed, 31 insertions, 4 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index 3923627c79..6d3361878b 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -3985,7 +3985,7 @@ The @code{local-file}, @code{plain-file}, @code{computed-file},
these objects lead to a file in the store. Consider this G-expression:
@example
-#~(system* (string-append #$glibc "/sbin/nscd") "-f"
+#~(system* #$(file-append glibc "/sbin/nscd") "-f"
#$(local-file "/tmp/my-nscd.conf"))
@end example
@@ -4044,7 +4044,7 @@ command:
(use-modules (guix gexp) (gnu packages base))
(gexp->script "list-files"
- #~(execl (string-append #$coreutils "/bin/ls")
+ #~(execl #$(file-append coreutils "/bin/ls")
"ls"))
@end example
@@ -4055,8 +4055,7 @@ executable file @file{/gnu/store/@dots{}-list-files} along these lines:
@example
#!/gnu/store/@dots{}-guile-2.0.11/bin/guile -ds
!#
-(execl (string-append "/gnu/store/@dots{}-coreutils-8.22"/bin/ls")
- "ls")
+(execl "/gnu/store/@dots{}-coreutils-8.22"/bin/ls" "ls")
@end example
@end deffn
@@ -4126,6 +4125,34 @@ as in:
This is the declarative counterpart of @code{text-file*}.
@end deffn
+@deffn {Scheme Procedure} file-append @var{obj} @var{suffix} @dots{}
+Return a file-like object that expands to the concatenation of @var{obj}
+and @var{suffix}, where @var{obj} is a lowerable object and each
+@var{suffix} is a string.
+
+As an example, consider this gexp:
+
+@example
+(gexp->script "run-uname"
+ #~(system* #$(file-append coreutils
+ "/bin/uname")))
+@end example
+
+The same effect could be achieved with:
+
+@example
+(gexp->script "run-uname"
+ #~(system* (string-append #$coreutils
+ "/bin/uname")))
+@end example
+
+There is one difference though: in the @code{file-append} case, the
+resulting script contains the absolute file name as a string, whereas in
+the second case, the resulting script contains a @code{(string-append
+@dots{})} expression to construct the file name @emph{at run time}.
+@end deffn
+
+
Of course, in addition to gexps embedded in ``host'' code, there are
also modules containing build tools. To make it clear that they are
meant to be used in the build stratum, these modules are kept in the