rpm: Query all installed packages.

在 Redhat/Fedora/SuSE 上查詢所有已經安裝的套件
可以使用

rpm -qa

如果想要查詢套件名稱含有某關鍵字的則可以使用

rpm -qa | grep kernel

或者是

rpm -qa '*kernel*'

自己習慣上都是使用

rpm -qa | grep kernel

(鍵盤比較好敲)
不過

rpm -qa '*kernel*'

似乎應該比較快速(就程式執行的速度來看)
於是就做了一個小實驗

$ for ((i=0;i<3;i++)); do time echo $(rpm -qa '*kernel*'); done
kernel-devel-2.6.19-1.2895.fc6 kernel-headers-2.6.19-1.2895.fc6 kernel-2.6.19-1.2895.fc6

real    0m2.856s
user    0m2.640s
sys     0m0.149s
kernel-devel-2.6.19-1.2895.fc6 kernel-headers-2.6.19-1.2895.fc6 kernel-2.6.19-1.2895.fc6

real    0m2.854s
user    0m2.656s
sys     0m0.138s
kernel-devel-2.6.19-1.2895.fc6 kernel-headers-2.6.19-1.2895.fc6 kernel-2.6.19-1.2895.fc6

real    0m2.858s
user    0m2.631s
sys     0m0.141s

$ for ((i=0;i<3;i++)); do time echo $(rpm -qa | grep kernel); done
kernel-devel-2.6.19-1.2895.fc6 kernel-headers-2.6.19-1.2895.fc6 kernel-2.6.19-1.2895.fc6

real    0m3.246s
user    0m2.738s
sys     0m0.448s
kernel-devel-2.6.19-1.2895.fc6 kernel-headers-2.6.19-1.2895.fc6 kernel-2.6.19-1.2895.fc6

real    0m3.381s
user    0m2.727s
sys     0m0.570s
kernel-devel-2.6.19-1.2895.fc6 kernel-headers-2.6.19-1.2895.fc6 kernel-2.6.19-1.2895.fc6

real    0m3.311s
user    0m2.705s
sys     0m0.546s

果然經過 pipeline 的方法比較慢~ :)