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...
ifgrep-q fooregex myfile;then...fi 如果grep 在 myfile 中找到匹配的行,它的执行结果为 0(true),then 后面的部分就会执行。 10. if [bar="$foo"]; then ... 正如上一个问题中提到的,[是一个命令,它的参数之间必须用空格分隔。 11. if [ [ a = b ] && [ c = d ] ]; then ... 不...
Thebashcommand fails with the following error: An error occurred mounting one of your file systems. Please run 'dmesg' for more details. Following these instructions, here is the relevant output fromdmesg: [ 73.412597] scsi 0:0:0:2: Direct-Access Msft Virtual Disk 1.0 PQ: 0 ANSI: 5 [ ...
9. if [grep foo myfile] 初学者会错误地认为,[是 if 语法的一部分,正如 C 语言中的 if 。但是事实并非如此,if 后面跟着的是一个命令,[是一个命令,它是内置命令 test 的简写形式,只不过它要求最后一个参数必须是]。下面两种写法是一样的: # POSIX if[false];thenecho"HELP";fi iftestfalse;thenecho...
# if cron fails or if you want backup on demand just run these commands # # again pass it via sudo so whoever is in admin group can start the job # # Backup scripts # alias backup = 'sudo /home/scripts/admin/scripts/backup/wrapper.backup.sh --type local --taget /raid1/backups'...
27. local varname=$(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 [[ $foo =~ 'some RE' ]] ...
You need to knowwhether the command you ran succeeded. Solution The shell variable$?is set with a nonzero value if the command fails—providedthat the programmer who wrote that command or shell script followed the established convention:
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, ...
值并发生重复赋值时,bash会覆盖该键。这 允许我们有效地删除数组重复。 CAVEAT:需要bash4+ 示例功能: remove_array_dups() { # Usage: remove_array_dups "array" declare -A tmp_array for i in "$@"; do [[ $i ]] && IFS=" " tmp_array["${i:- }"]=1 ...
value of the $location variable is not evaluatedaz group create--name$resourceGroup--location$location# Notice that the space in the $location variable is not ignored and the command fails as it treats the value after the space as a new commandaz group create--name$resourceGroup--location"$...