Differences
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scripting:processtree [2019/08/30 14:45] ersen [The process tree] |
scripting:processtree [2019/08/30 14:55] (current) ersen [Bash playing with pipes] |
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| - | Note once again, ''ls'' can't influence the ''grep'' environment. ''grep'' can't influence the ''ls'' environmet, and neither ''grep'' nor ''ls'' can influence the ''bash'' environment. | + | Note once again, ''ls'' can't influence the ''grep'' environment, ''grep'' can't influence the ''ls'' environment, and neither ''grep'' nor ''ls'' can influence the ''bash'' environment. |
| __**How is that related to shell programming?!?**__ | __**How is that related to shell programming?!?**__ | ||
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| </code> | </code> | ||
| - | See the relationship? The forked Bash process will count the lines like a charm. It will also set the variable ''counter'' as directed. But if everything ends, this extra process will be terminated - **your "counter" variable is gone** You see a 0 because in the main shell it was 0, and wasn't changed by the child process! | + | See the relationship? The forked Bash process will count the lines like a charm. It will also set the variable ''counter'' as directed. But if everything ends, this extra process will be terminated - **your "counter" variable is gone.** You see a 0 because in the main shell it was 0, and wasn't changed by the child process! |
| __**So, how do we count the lines?**__ | __**So, how do we count the lines?**__ | ||
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| </code> | </code> | ||
| - | It's nearly self-explanitory. The ''while'' loop runs in the **current shell**, the counter is incremented in the **current shell**, everything vital happens in the **current shell**, also the ''read'' command sets the variable ''REPLY'' (the default if nothing is given), though we don't use it here. | + | It's nearly self-explanatory. The ''while'' loop runs in the **current shell**, the counter is incremented in the **current shell**, everything vital happens in the **current shell**, also the ''read'' command sets the variable ''REPLY'' (the default if nothing is given), though we don't use it here. |
| ===== Actions that create a subshell ===== | ===== Actions that create a subshell ===== | ||