From: W. Trevor King <wking@tremily.us>
Date: Fri, 22 Mar 2013 05:38:23 +0000 (-0400)
Subject: data-file-descriptor.gp: Fead from a file descriptor with '<&n'
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=refs%2Fheads%2Fnote%2Fgnuplot;p=assignment-template.git

data-file-descriptor.gp: Fead from a file descriptor with '<&n'

My patch was accepted into 4.6.2 :).
---

diff --git a/Makefile b/Makefile
index fb6c7de..d971545 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,8 @@
 
 # The target of the first rule is the default goal.  See:
 #   http://www.gnu.org/software/make/manual/html_node/Rules.html
-all: data-file.png data-stdin.png everything-stdin.png data-command.png
+all: data-file.png data-stdin.png data-file-descriptor.png \
+		everything-stdin.png data-command.png
 
 # Generate an example data file
 # For an explanation of $<, $@, and other special variables, see
@@ -19,6 +20,10 @@ data-file.png: data-file.gp sine.data
 data-stdin.png: data-stdin.gp sine.py
 	./sine.py | gnuplot "$<" > "$@"
 
+# No data filename required
+data-file-descriptor.png: data-file-descriptor.gp sine.data
+	gnuplot "$<" 4<sine.data > "$@"
+
 # No data file required
 everything-stdin.png: everything-stdin.gp sine.py
 	(cat "$<"; ./sine.py) | gnuplot > "$@"
diff --git a/data-file-descriptor.gp b/data-file-descriptor.gp
new file mode 100644
index 0000000..f9b9589
--- /dev/null
+++ b/data-file-descriptor.gp
@@ -0,0 +1,15 @@
+# Gnuplot (since v4.6.2) can read the script from a file and data from
+# an arbitrary file descriptor.  This is useful when you want to plot
+# several data files with the same script, since you don't need to
+# hard-code the filename in the script itself.
+
+set term png
+set title 'Plotting data from a file descriptor'
+set xlabel 'x'
+set ylabel 'f(x)'
+
+# gnuplot> help special-filenames
+plot '<&4' t 'sin(x)'
+
+# the '<&4' syntax is reading from file descriptor 4.  See `help
+# special-filenames` for details.
diff --git a/data-stdin.gp b/data-stdin.gp
index d1d72a4..47436ef 100644
--- a/data-stdin.gp
+++ b/data-stdin.gp
@@ -8,7 +8,4 @@ set ylabel 'f(x)'
 # gnuplot> help special-filenames
 plot '< cat' t 'sin(x)'
 
-# the `cat` command is reading from stdin.  There does not seem to be
-# a way to read from an arbitrary file descriptor without using the
-# '< COMMAND' syntax, although I just submitted a patch to add it:
-#    https://sourceforge.net/tracker/?func=detail&aid=3600849&group_id=2055&atid=302055
+# the `cat` command is reading from stdin.