使用 exec 对 c 中的文本文件进行排序
我有一个充满记录的文本文件 (output.txt)，我想按 ID 对每个记录进行排序。排序后，排序后的记录将写入新文件（sorted.txt）。
为此，我通过 execl() 函数使用 bash 的命令“sort”。为了检查排序命令的有效性，我将相同的命令直接写入 bash，结果是预期的。但是当我尝试通过我的 C 程序使用 execl 命令时，大多数时候答案是没有文件 /usr/bin/sort （我使用的是 Mac OSX）或者不会抛出错误消息，但尽管如此什么也没发生... 我正在使用的是这样的：
execl("/usr/bin/sort", "usr/bin/sort", "-n","-k", "1", "-u", "output.txt", ">", "sorted.txt", (char*)NULL);
或者
execl("/usr/bin/sort", "usr/bin/sort", "-n","-k", "1", "-u", "-o", "sorted.txt", "output.txt", (char*)NULL);
我知道当我在 bash 中使用这两个排序命令时它们都是正确的。 C 会发生什么事？ 提前谢谢大家！
I have a text file full of records (output.txt) and I want to sort every record by its id. After the sorting the sorted records are written into a new file (sorted.txt).
To do that I am using bash's command "sort" via an execl() function. To check the validity of my sort command, I wrote the same command straight into the bash and the result is the expected one. But when I try to use the execl command through my C program, most of the time the answer will be that there is not a file /usr/bin/sort (I am using Mac OSX) or no error message will be thrown but nevertheless nothing happens...
What I am using is this:
execl("/usr/bin/sort", "usr/bin/sort", "-n","-k", "1", "-u", "output.txt", ">", "sorted.txt", (char*)NULL);
or this
execl("/usr/bin/sort", "usr/bin/sort", "-n","-k", "1", "-u", "-o", "sorted.txt", "output.txt", (char*)NULL);
I know that both of these 2 sort commands are correct when I m using them in the bash. What happens to C?
Thnx all in advance!
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输出重定向（
> somefile.txt）是 shell 的一项功能，而不是排序程序（AFAIK 不是 bash 内置的）。exec系列函数不会启动 shell，只会启动您指定的程序。如果您不知道程序的路径，您可以使用名称中带有
p的函数（我认为在您的情况下是execlp），然后给它们 < code>"sort" 作为程序名称，它们会像 bash 一样在 $PATH 中搜索它。Output redirection (
> somefile.txt) is a feature of the shell, not the sort program (which AFAIK is not a bash built-in).The
execfamily of functions doesn't start the shell, only the program you've specified.If you don't know the path to the program, you can use the functions with
pin their names (execlpin your case, I think) and just give them"sort"as program name, they'll search for it in $PATH like bash does.或者，您可以尝试
system("sort output.txt >sorted.txt")。system函数的行为取决于实现，但在 Linux 上它基本上会生成一个新的 shell 来执行传递给它的命令。system(ARG)相当于sh -c ARG。如果 shell 在系统的system函数实现中支持重定向，则重定向将起作用。Alternatively you can try
system("sort output.txt > sorted.txt"). Thesystemfunction's behaviour is implementation dependent though on linux it basically spawns a new shell which executes the command passed to it.system(ARG)is equivalent tosh -c ARG. The redirection will work if the shell supports it in your system's implementation of thesystemfunction.