bash 使用 gnuplot 编写脚本——在 sed 处
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Scripting with gnuplot--where sed
提问by Samuel Markson
So I'm looking for some quick-and-dirty solution.
所以我正在寻找一些快速而肮脏的解决方案。
The problem:
问题：
I am trying to plot a specific section of a data file with gnuplot. This is fine. The basic line goes something like
我正在尝试使用 gnuplot 绘制数据文件的特定部分。这可以。基本路线类似于
plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:log(**2+**2) notitle
This works just fine. The next step I want is to include in my title another part of the data, namely the data entry $3 (which for the points listed is identical, so I can parse it from anywhere). I run into problem because, while plot seems fine, I can't seem to feed regex info into 'title'. An example of something that doesn'twork"
这工作得很好。我想要的下一步是在我的标题中包含另一部分数据，即数据条目 $3（对于列出的点来说是相同的，所以我可以从任何地方解析它）。我遇到了问题，因为虽然情节看起来不错，但我似乎无法将正则表达式信息输入到“标题”中。一个不起作用的例子”
plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:log(**2+**2) title "<(sed -n '1,1p' pointsandstuff.dat)"
(This would spit out a whole data line, in theory, though in practice I just get the title "<(sed...")
（理论上，这会吐出一整条数据线，但实际上我只会得到标题“<（sed ...”）
I tried attacking this with a bash script, but the '$'s that I use throw the bash script into a tizzy:
我尝试用 bash 脚本攻击它，但是我使用的“$”使 bash 脚本陷入困境：
#!/bin/bash
STRING=$(echo|sed -n '25001,25001p' pointsandstuff.dat)
echo $STRING
gnuplot -persist << EOF
set xrange[:] noreverse nowriteback
set yrange[:] noreverse nowriteback
eval "plot "<(sed -n '25001,30000p' pointsandstuff.dat)" u 1:log(**2+**2) title $STRING
EOF
Bash won't know what to do with '$4' and '$5'.
Bash 不知道如何处理“$4”和“$5”。
采纳答案by Samuel Markson
Aha, thanks all. Have come up with a few solutions by now--the simplest being just escaping those $s from before (which I mistakenly thought gnuplot disliked...). To whit:
啊哈，谢谢大家。现在已经想出了一些解决方案——最简单的就是从之前转义那些 $s（我错误地认为 gnuplot 不喜欢......）。至于：
STRING=$(echo|sed -n '1,1p' spointsandstuff.dat)
echo $STRING
gnuplot -persist << EOF
set xrange[:] noreverse nowriteback
set yrange[:] noreverse nowriteback
eval "plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:(log($4**2+$5**2)) title '$STRING'
!gv diag_spec.eps &
EOF
Thanks all, though--it's been a good excuse to play with this stuff...here's hoping that, if any poor soul sees this script later, it might be a bit easier on them.
不过，谢谢大家——这是玩这些东西的一个很好的借口……这里希望，如果以后有任何可怜的人看到这个脚本，对他们来说可能会容易一些。
回答by Jonathan Leffler
You seem to be attempting process substitution, but the double quotes stop it working in the first case and you need a command substitution in the second case.
您似乎正在尝试进程替换，但双引号使其在第一种情况下停止工作，而在第二种情况下您需要命令替换。
You have:
你有：
plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:log(**2+**2) \
title "<(sed -n '1,1p' pointsandstuff.dat)"
You need:
你需要：
plot <(sed -n '1,100p' pointsandstuff.dat) u 1:log(**2+**2) \
title "$(sed -n '1,1p' pointsandstuff.dat)"
The double quotes in the second case might not be strictly necessary, but you won't go wrong with them present.
第二种情况下的双引号可能不是绝对必要的，但你不会出错。
Process substitution generates a file name and feeds the output of the nested command into that file; the command thinks it is reading a file (because it is reading a file).
Command substitution captures the output of the nested command in a string and passes that string to the command (when it is used as an argument to a command, as here).
进程替换生成一个文件名，并将嵌套命令的输出提供给该文件；该命令认为它正在读取一个文件（因为它正在读取一个文件）。
命令替换捕获字符串中嵌套命令的输出并将该字符串传递给命令（当它用作命令的参数时，如下所示）。
回答by mgilson
My understanding of the question is a little hazy, but it looks like you want to plot the first 100 lines -- This is quite easy to do:
我对这个问题的理解有点模糊，但看起来你想绘制前 100 行——这很容易做到：
plot '< head -100 datafile.dat' u ....
Of course, you can use sedif you wish (or awkor ...). A gnuplot only solution might look like this:
当然，sed如果您愿意（或awk或...），您可以使用。仅 gnuplot 的解决方案可能如下所示：
plot 'datafile.dat' u (plot 'datafile.dat' every ::25001::30000 u 1:(log(**2+**2)
> 100? 1/0:):(log(**2+**2))
Or like this (which is more simple for regular selections):
或者像这样（对于常规选择更简单）：
plot ... title "`head -1 datafile.dat | awk '{print }'`"
and explained in more detail in another answer.
并在另一个答案中更详细地解释。
Now, if you want the title to come from the datafile, you can parse it out using gnuplot's backtic substitution:
现在，如果您希望标题来自数据文件，您可以使用 gnuplot 解析它backtic substitution：
plot ... title system("head -1 datafile.dat | awk '{print }'")
which is essentially the same as gnuplot's system command:
本质上与 gnuplot 的系统命令相同：
plot ... title columnhead(3)
but in this case, you mightbe able to use the columnheadfunction:
但在这种情况下，您可能可以使用该columnhead功能：
