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$ echo “This, is, a, test, to, remove, commas.” | > sed -n ‘{ > :start > s/,//1p > t start > }’ This is, a, test, to, remove, commas. This is a, test, to, remove, commas. This is a test, to, remove, commas. This is a test to, remove, commas. This is a test to remove, commas. This is a test to remove commas. $ 当没有逗号可替换时，测试命令不再跳转，而是继续执行剩下的脚本（在本例中，也就是结束脚本）。
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Linux命令行与shell脚本编程大全