9. if [grep foo myfile] 初学者会错误地认为,[是 if 语法的一部分,正如 C 语言中的 if ()。但是事实并非如此,if 后面跟着的是一个命令,[是一个命令,它是内置命令 test 的简写形式,只不过它要求最后一个参数必须是]。下面两种写法是一样的: # POSIX if [ false ]; then echo "HELP"; fi if tes...
# POSIXforiin*.mp3;do[-e"$i"] || continue some command"$i"done 1. 2. 3. 4. 5. 如果你有使用引号[6]和避免单词拆分[7]的习惯,你完全可以避免很多错误。 注意下循环体内部的 "$i",这里会导致下面我们要说的另外一个比较容易犯的错误。 2. cp $file $target 上面的命令有什么问题呢?如果你...
9. if [grep foo myfile] 初学者会错误地认为,[是 if 语法的一部分,正如 C 语言中的 if 。但是事实并非如此,if 后面跟着的是一个命令,[是一个命令,它是内置命令 test 的简写形式,只不过它要求最后一个参数必须是]。下面两种写法是一样的: # POSIX if[false];thenecho"HELP";fi iftestfalse;thenecho...
ifCOMMANDSthen<COMMANDS>elif<COMMANDS># optional then<COMMANDS>else<COMMANDS># optional fi # required 再次强调,[是一个命令,它同其它常规的命令一样接受参数。if 是一个复合命令,它包含其它命令,[并不是 if 语法中的一部分。 如果你想根据 grep 命令的结果来做事情,你不需要把 grep 放到 [里面,只需要在...
27. local varname=$(command) 28. export foo=~/bar 29. sed 's/$foo/good bye/' 30. tr [A-Z] [a-z] 31. ps ax | grep gedit 32. printf "$foo" 33. for i in {1..$n} 34. if [[ $foo = $bar ]] 35. if [[ $foo =~ 'some RE' ]] ...
command(1) comp_err(1) compare(1) composite(1) compress(1) config.guess(1) config.sub(1) config_data(1) conflict(1) conjure(1) constype(1) continue(1) convert(1) convmv(1) corelist(1) cp(1) cp(1g) cpack(1) cpan(1) cpan2dist(1) cpanp(1) cpio(1) cpp(1) cpp(1) cpu...
Version 3.7.2 2005/11/16 作者:Mendel Cooper mail:thegrendel@theriver.com 这本书假定你没有任何脚本或一般程序的编程知识,但是如果你有相关的知识,那么你将很容易 达到中高级的水平...all the while sneaking in little snippets of UNIX? wisdom and lor... ...
Suppose this method isn't doing the trick, continue reading the next one to resolve the "zsh: command not found" error on your M1 Mac or Intel Mac. Reinstall macOS or restore from Time Machine If you were digging around in the system and happened to delete some system files or folders,...
You noticed there's an added retry to thescpcommand. But that retries only for failed connections, what if the command fails during the middle of the copy? Sometimes you want to just fail because there's very little chance to recover from an issue. A system that requires hardware fixes, ...
sudocommand Some Bash commands can only be run by the root user; a system administrator or superuser. If you try one of these commands without sufficient privileges, it fails. For example, only users logged in as a superuser can usecatto display the contents of/etc/at.deny: ...