fro*_*age 5 command-line bash limit readline here-document
使用 here-docs 作为bash命令行的一部分有什么长度限制？我发现简短的 here-docs 工作得很好，但是当它们变长时，就会出现某些点或结构，然后它们就会中断。当它失败时，有两个症状。一是here-doc被提前放弃。另一种是输出中的一个或多个here-doc行被截断，不一定是最后一行。
下面你会看到一个人为的示例命令，我可以用它来重现问题。here-doc 是乏味的 58 行，每行包含 79 个“x”字符和一个换行符。如果我将所有 60 行（不包括 , 中的换行符）复制并粘贴EOF到交互式bashshell，那么我必须手动点击Enter并且整个命令每次都会成功运行。但是，如果我复制和粘贴的所有60线，其中包括了EOF新行，那么这是在发生故障时。如果我在桌面上的终端应用程序中执行后者，它总是失败。如果我在远程 SSH 客户端执行此操作，它有时会工作，有时会失败。显着减少 here-doc 行的数量，问题就消失了。中途放弃 here-doc 意味着所有剩余的 here-doc 行和该EOF行都被视为bash新的单独命令行，这只会导致一系列“未找到命令”错误（或者可能更糟，如果here-doc 包含合法的命令行）。
cat > ~/test.txt << 'EOF'
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EOF
我知道bash有命令行长度限制，但这个例子远低于这些限制。事实上，上述多行命令中的任何一行都不会超过 80 个字符，而且每一行都从 shell 获得自己的提示，所以我什至不确定会应用什么限制。对我来说，here-doc 的长度应该受到限制似乎很奇怪。
我正在使用 Linux Mint 17（Ubuntu 14.04）。
$ bash --version
GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu)
...
$ uname -a
Linux QWERTY 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
在 bash 脚本中使用此类命令时不会发生此问题。
我不知道这里文档有任何大小限制。我正在运行kernel 3.9.1，并且在这里遇到了同样的问题：在终端中粘贴大块文本时，某些行被截断或丢失。我发现（经过一番谷歌搜索），如果您关闭行编辑，粘贴效果很好（此处讨论：将大量文本粘贴到启用读取行的程序中会截断所粘贴文本的部分行）。
进一步的调查表明，这个问题的根源实际上是一个内核错误（drivers/tty），并且显然它已在内核 >= 3.14 中修复。这可能解释了为什么安装了更多最新版本的人无法复制我们都经历过的行为。
更新：
我可以确认安装后kernel 3.16.6一切正常，因此修补内核或升级到更新的版本（>=3.14）应该可以解决此问题。