os_cp:pipes_signals
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os_cp:pipes_signals [2023/04/18 23:50] jkonczak utworzono |
os_cp:pipes_signals [2023/05/09 23:18] (current) jkonczak [Shared memory] |
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| <small> You may do this e.g., by: ''pipe'', ''fork'', in one process: ''dup2'' | <small> You may do this e.g., by: ''pipe'', ''fork'', in one process: ''dup2'' | ||
| - | and ''exec'', in the other process: reading from pipe and changing case.</small> | + | and ''exec'', in the other process: reading from pipe and changing case. |
| + | \\ | ||
| + | The ''[[https://en.cppreference.com/w/c/string/byte/toupper|toupper]]'' function (available from ''ctype.h'') converts a single character to upper case. | ||
| - | ~~Exercise.#~~ Write a program that does ''ps -eF | sort -nk6''. | + | ~~Exercise.#~~ Write a program that does ''ps -eF | sort -nk6''.</small> |
| ===== Signals ===== | ===== Signals ===== | ||
| - | Disclaimer: these materials contain the very basics signals. | + | Disclaimer: these materials contain the very basics of signals. |
| - | For a comprehensive information on signals, see the | + | For comprehensive informations, see the |
| [[https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04|POSIX standard]]. | [[https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04|POSIX standard]]. | ||
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| To ensure that the file is large enough, one can use the following functions: | To ensure that the file is large enough, one can use the following functions: | ||
| * ''[[https://pubs.opengroup.org/onlinepubs/9699919799/functions/ftruncate.html|ftruncate]]'' <html><span style="float:right"><small>Needs header: <code>unistd.h</code></small></span></html> resizes file to a given size. \\ Whenever the file is larger it is truncated. | * ''[[https://pubs.opengroup.org/onlinepubs/9699919799/functions/ftruncate.html|ftruncate]]'' <html><span style="float:right"><small>Needs header: <code>unistd.h</code></small></span></html> resizes file to a given size. \\ Whenever the file is larger it is truncated. | ||
| - | * ''[[https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_fallocate.html|posix_fallocate]]'' <html><span style="float:right"><small>Needs header: <code>fcntl.h</code></small></span></html> ensures that the file at least of a given size. \\ Whenever the file is larger it is left unchanged. \\ <small>Warning: ''posix_fallocate'' is guaranteed to work for ordinary files. Result of using ''posix_fallocate'' on shared memory object is undefined.</small> | + | * ''[[https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_fallocate.html|posix_fallocate]]'' <html><span style="float:right"><small>Needs header: <code>fcntl.h</code></small></span></html> ensures that the file at least of a given size. \\ Whenever the file is larger it is left unchanged. \\ <small>Warning: ''posix_fallocate'' is guaranteed to work for ordinary files. The result of using ''posix_fallocate'' on a shared memory object is undefined.</small> |
| To clean up the memory mapping, one has to use the | To clean up the memory mapping, one has to use the | ||
| Line 441: | Line 443: | ||
| <html><p style="text-align: center"><object id="svg-object" data="/jkonczak/_media/os_cp:mmap.svg" type="image/svg+xml"></object></p></html> | <html><p style="text-align: center"><object id="svg-object" data="/jkonczak/_media/os_cp:mmap.svg" type="image/svg+xml"></object></p></html> | ||
| + | |||
| + | **To compile programs that use ''shm_open'' with older glibc versions, one must add ''-lrt'' to compile options.** | ||
| ~~Exercise.#~~ | ~~Exercise.#~~ | ||
| Line 497: | Line 501: | ||
| char c, text[1022] = {0}; | char c, text[1022] = {0}; | ||
| - | scanf("%[^\n]1021", text); | + | scanf("%1021[^\n]", text); |
| do { // this reads all remaining characters in this line including '\n' | do { // this reads all remaining characters in this line including '\n' | ||
| c = getchar(); | c = getchar(); | ||
| Line 575: | Line 579: | ||
| } | } | ||
| </code> | </code> | ||
| - | |||
| - | //one must use msync() | ||
| - | //to sync data to disk | ||
| ~~META: | ~~META: | ||
os_cp/pipes_signals.1681854603.txt.gz · Last modified: 2023/04/18 23:50 (external edit)
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