os_cp:files_processes
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os_cp:files_processes [2024/03/05 14:51] jkonczak [Hard and soft links] |
os_cp:files_processes [2025/03/12 21:03] (current) jkonczak |
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| ===== Copying, moving and erasing files ===== | ===== Copying, moving and erasing files ===== | ||
| - | <html><small></html> | + | <small> |
| - | To create an empty file, you can use ''touch //file//''. To create file with some contents, you can use ''echo //contents// > //file//'' or ''fortune > //file//''. | + | To create an empty file, you can use ''touch //file//''. |
| + | To create file with some contents, you can use ''echo //contents// > //file//'' | ||
| + | or ''fortune > //file//''. | ||
| \\ | \\ | ||
| The ''touch'' and ''echo'' commands as well as meaning of ''>'' will be explained later on. | The ''touch'' and ''echo'' commands as well as meaning of ''>'' will be explained later on. | ||
| Line 11: | Line 13: | ||
| To display a file, use ''cat //filename//''. | To display a file, use ''cat //filename//''. | ||
| - | <html></small></html> | + | </small> |
| ==== Directories ==== | ==== Directories ==== | ||
| Line 17: | Line 19: | ||
| **''mkdir //dir//''** creates a new directory. | **''mkdir //dir//''** creates a new directory. | ||
| \\ | \\ | ||
| - | <html><small></html> | + | <small> |
| ''mkdir -p //dir1/dir2/dir3//'' creates directory ''dir1'', and directory ''dir2'' within ''dir1'', and ''dir3'' within ''dir1/dir2''. | ''mkdir -p //dir1/dir2/dir3//'' creates directory ''dir1'', and directory ''dir2'' within ''dir1'', and ''dir3'' within ''dir1/dir2''. | ||
| \\ | \\ | ||
| With the ''-p'' switch ''mkdir'' does not print an error if a directory already exists. | With the ''-p'' switch ''mkdir'' does not print an error if a directory already exists. | ||
| - | <html></small></html> | + | </small> |
| To remove an empty directory one can use ''rmdir //dir//''. | To remove an empty directory one can use ''rmdir //dir//''. | ||
| ~~Exercise.#~~ Create the following directory tree: | ~~Exercise.#~~ Create the following directory tree: | ||
| + | <html><pre style="margin-top:-1.2em"> | ||
| . | . | ||
| ├── foo | ├── foo | ||
| Line 33: | Line 36: | ||
| └── foobaz | └── foobaz | ||
| └── bar | └── bar | ||
| - | + | </pre></html> | |
| ~~Exercise.#~~ Remove ''foo/baz'' directory | ~~Exercise.#~~ Remove ''foo/baz'' directory | ||
| Line 48: | Line 52: | ||
| ~~Exercise.#~~ Create a file ''file1'' with some contents. Create a hard link called ''file2'' of the file ''file1''. Modify ''file2''. Display ''file1''. | ~~Exercise.#~~ Create a file ''file1'' with some contents. Create a hard link called ''file2'' of the file ''file1''. Modify ''file2''. Display ''file1''. | ||
| - | <html><small></html> | + | <small> |
| ~~Exercise.#~~ The ''ls'' command can display link count for each listed file. Discover how to do it. | ~~Exercise.#~~ The ''ls'' command can display link count for each listed file. Discover how to do it. | ||
| Line 54: | Line 58: | ||
| The disk space used by a file is reclamied once link count drops to 0 (all directory entries that link to the file are erased) and the file is no longer open in any process. | The disk space used by a file is reclamied once link count drops to 0 (all directory entries that link to the file are erased) and the file is no longer open in any process. | ||
| - | <html></small></html> | + | </small> |
| ~~Exercise.#~~ Create in your home directory a symlink called ''TMP'' pointing to ''/tmp''. Change directory to ''TMP''. What does ''pwd'' output? | ~~Exercise.#~~ Create in your home directory a symlink called ''TMP'' pointing to ''/tmp''. Change directory to ''TMP''. What does ''pwd'' output? | ||
| Line 62: | Line 66: | ||
| ~~Exercise.#~~ Create a symlink to a non-existent path. List the directory containing it. | ~~Exercise.#~~ Create a symlink to a non-existent path. List the directory containing it. | ||
| - | <html><small></html> | + | <small> |
| - | The ''readlink [-f] //target//'' command resolves all symlinks and prints a [[https://en.wikipedia.org/wiki/Canonicalization|canonical]] path. | + | The commands ''readlink [-f] //target//'' and ''realpath -e //target//'' resolve all |
| + | symlinks and print a [[https://en.wikipedia.org/wiki/Canonicalization|canonical]] path. | ||
| The Windows NTFS filesystem supports links as well. Creating the links is possible e.g., with [[https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/mklink|mklink]] command. | The Windows NTFS filesystem supports links as well. Creating the links is possible e.g., with [[https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/mklink|mklink]] command. | ||
| - | <html></small></html> | + | </small> |
| ==== Copying and moving files ==== | ==== Copying and moving files ==== | ||
| Line 78: | Line 83: | ||
| The basic syntax is ''cp/mv //source//… //destination//''. \\ | The basic syntax is ''cp/mv //source//… //destination//''. \\ | ||
| Multiple source files can be provided if the destination is a directory. \\ | Multiple source files can be provided if the destination is a directory. \\ | ||
| - | If the destination is a file, it will be overwritten without warning <html><small></html>(unless ''-i'' or ''-n'' switch is used)<html></small></html>. | + | If the destination is a file, it will be overwritten without warning <small>(unless ''-i'' or ''-n'' switch is used)</small>. |
| - | <html><small></html> | + | <small> |
| By default ''cp'' will deny copying a directory. Use ''-r'' to copy a directory recursively. | By default ''cp'' will deny copying a directory. Use ''-r'' to copy a directory recursively. | ||
| - | <html></small></html> | + | </small> |
| When ''cp'' copies a file, it creates a new file with the current date, default permissions, etc. | When ''cp'' copies a file, it creates a new file with the current date, default permissions, etc. | ||
| Line 90: | Line 95: | ||
| To copy recursively, and preserve dates, permissions and more, one can use the **''-a''** switch (that stands for ''--archive''). | To copy recursively, and preserve dates, permissions and more, one can use the **''-a''** switch (that stands for ''--archive''). | ||
| - | <html><small></html> | + | <small> |
| With the ''-l'' switch ''cp'' creates a hard link instead of copying a file. Notice that this can be combined with ''--recursive''. | With the ''-l'' switch ''cp'' creates a hard link instead of copying a file. Notice that this can be combined with ''--recursive''. | ||
| - | <html></small></html> | + | </small> |
| ~~Exercise.#~~ Copy, using a single command, the files ''/etc/os-release'' and ''/etc/SUSE-brand'' to the current working directory. | ~~Exercise.#~~ Copy, using a single command, the files ''/etc/os-release'' and ''/etc/SUSE-brand'' to the current working directory. | ||
| Line 106: | Line 111: | ||
| ~~Exercise.#~~ Rename ''someDir'' to a name of your choice. | ~~Exercise.#~~ Rename ''someDir'' to a name of your choice. | ||
| - | <html><small></html> | + | <small> |
| - | ~~Exercise.#~~ Copy the renamed directory with ''-al'' switches. Modify a selected file with any of the directories. Which files changed contents? <html><small></html> \\ (You can ''cat //filename//'' or display modification dates with second accuracy using ''ls -l --time-style=+%H:%M:%S …'' or ''tree -D --timefmt=%H:%M:%S …'')<html></small></html> | + | ~~Exercise.#~~ Copy the renamed directory with ''-al'' switches. Modify a selected file with any of the directories. Which files changed contents? |
| + | \\ (You can ''cat //filename//'' or display modification dates with second accuracy using ''ls -l --time-style=+%H:%M:%S …'' or ''tree -D --timefmt=%H:%M:%S …'') | ||
| + | |||
| + | </small> | ||
| === [extra] Copying files to/from a remote machine === | === [extra] Copying files to/from a remote machine === | ||
| Line 116: | Line 124: | ||
| ''scp'' accepts the ''-r'' switch for copying recursively. | ''scp'' accepts the ''-r'' switch for copying recursively. | ||
| - | <html><small></html> | + | <small> |
| Microsoft Windows now ships with ''scp'' command, but usually [[https://en.wikipedia.org/wiki/Comparison_of_FTP_client_software#Protocol_support|various file commanders]] are more convenient. | Microsoft Windows now ships with ''scp'' command, but usually [[https://en.wikipedia.org/wiki/Comparison_of_FTP_client_software#Protocol_support|various file commanders]] are more convenient. | ||
| - | <html></small></html> | + | </small> |
| Most SSH servers enable also the SFTP protocol that allows copying files more conveniently.\\ | Most SSH servers enable also the SFTP protocol that allows copying files more conveniently.\\ | ||
| Line 131: | Line 139: | ||
| ~~Exercise.#~~ Copy the file to ''/tmp'' directory on another computer using ''sftp''. | ~~Exercise.#~~ Copy the file to ''/tmp'' directory on another computer using ''sftp''. | ||
| - | <html><small></html> | ||
| - | === Rsync === | ||
| - | The ''[[https://en.wikipedia.org/wiki/Rsync|rsync]]'' program is widely used to copy files and directories. It efficiently compares source files with destination files and copies only the differences. It can copy data to/from remote machines, and can compress the data sent via network to increase throughput. ''rsync'' is also commonly used to make backups. | + | === [extra] Rsync === |
| - | <html></small></html> | + | The ''[[https://en.wikipedia.org/wiki/Rsync|rsync]]'' program is widely used to copy files and directories. It efficiently compares source files with destination files and copies only the differences. It can copy data to/from remote machines, and can compress the data sent via network to increase throughput. ''rsync'' is also commonly used to make backups. |
| - | <html></small></html> | ||
| ==== Removing files ==== | ==== Removing files ==== | ||
| Line 180: | Line 185: | ||
| ~~Exercise.#~~ Measure how long it took to execute the command in the previous example. | ~~Exercise.#~~ Measure how long it took to execute the command in the previous example. | ||
| - | |||
| <small> | <small> | ||
| + | |||
| ~~Exercise.#~~ Tell how long it takes to execute the ''openssl dhparam -text 1536'' command. | ~~Exercise.#~~ Tell how long it takes to execute the ''openssl dhparam -text 1536'' command. | ||
| ~~Exercise.#~~ Run the ''openssl dhparam -text 2048'' command with 5s run limit. | ~~Exercise.#~~ Run the ''openssl dhparam -text 2048'' command with 5s run limit. | ||
| + | |||
| </small> | </small> | ||
| Line 237: | Line 243: | ||
| </small> | </small> | ||
| - | ==== Getting information on currently run processes ==== | + | ==== Getting information on currently running processes ==== |
| === List of processes === | === List of processes === | ||
| Line 250: | Line 256: | ||
| <small> | <small> | ||
| + | |||
| The ''ps'' program has two allowed command syntaxes — one typical for UNIX programs, one with its roots in BSD. | The ''ps'' program has two allowed command syntaxes — one typical for UNIX programs, one with its roots in BSD. | ||
| \\ | \\ | ||
| The ubiquitous ''ps aux'' command is an example of ''ps'' run with BSD-style options | The ubiquitous ''ps aux'' command is an example of ''ps'' run with BSD-style options | ||
| that show all processes in a specific format. | that show all processes in a specific format. | ||
| + | |||
| </small> | </small> | ||
| Line 306: | Line 314: | ||
| </small> | </small> | ||
| - | <html><small></html> | ||
| === [extra] Live process viewers === | === [extra] Live process viewers === | ||
| Line 341: | Line 348: | ||
| There are numerous ''top''-inspired programs. These include ''iotop'' (for I/O), | There are numerous ''top''-inspired programs. These include ''iotop'' (for I/O), | ||
| ''atop'' and ''glances''. | ''atop'' and ''glances''. | ||
| - | |||
| - | <html></small></html> | ||
| === Looking up process identifiers === | === Looking up process identifiers === | ||
| Line 357: | Line 362: | ||
| The ''pidof //name//'' command outputs pids of processes whose executable name (trimmed to 15 characters) | The ''pidof //name//'' command outputs pids of processes whose executable name (trimmed to 15 characters) | ||
| is identical to the provided name. | is identical to the provided name. | ||
| + | |||
| </small> | </small> | ||
| Line 374: | Line 380: | ||
| role for processes as interrupts do for the operating system — they notify | role for processes as interrupts do for the operating system — they notify | ||
| a process about an external event by forcefully switching the control flow of | a process about an external event by forcefully switching the control flow of | ||
| - | one of the processes threads to a signal handler. | + | one of the process's threads to a signal handler. |
| \\ | \\ | ||
| The programmer can choose to block or ignore specified signals and may set up | The programmer can choose to block or ignore specified signals and may set up | ||
| Line 429: | Line 435: | ||
| Switches allow comparing against full executable name, and using regular | Switches allow comparing against full executable name, and using regular | ||
| expressions. | expressions. | ||
| + | |||
| </small> | </small> | ||
| Line 436: | Line 443: | ||
| <small> | <small> | ||
| + | |||
| ~~Exercise.#~~ In one terminal run a DNS server with the ''named -g -c <(:)'' command. From another terminal send a HUP signal to ''named''. How did it react? | ~~Exercise.#~~ In one terminal run a DNS server with the ''named -g -c <(:)'' command. From another terminal send a HUP signal to ''named''. How did it react? | ||
| - | </small> | ||
| - | <html><small></html> | + | </small> |
| ==== [extra] Controlling process scheduling ==== | ==== [extra] Controlling process scheduling ==== | ||
| Line 493: | Line 500: | ||
| ~~Exercise.#~~ In two terminals run ''taskset -pc 0 $$'' (<small>that lets this shell and its children use only first physical thread</small>). | ~~Exercise.#~~ In two terminals run ''taskset -pc 0 $$'' (<small>that lets this shell and its children use only first physical thread</small>). | ||
| \\ | \\ | ||
| - | Then, in both terminals, run ''openssl dhparam -text %%$((2**14))%% [//arbitrary text//]'' | + | Then, in both terminals, run ''openssl dhparam -text %%$((2**13))%%'' |
| (<small>this starts some CPU-intensive computations</small>). | (<small>this starts some CPU-intensive computations</small>). | ||
| \\ | \\ | ||
| Line 538: | Line 545: | ||
| on physical threads of node //x// and memory of node //y//. | on physical threads of node //x// and memory of node //y//. | ||
| - | <html></small></html> | ||
| Line 544: | Line 550: | ||
| language = en | language = en | ||
| ~~ | ~~ | ||
| - | |||
| - | |||
os_cp/files_processes.1709646706.txt.gz · Last modified: 2024/03/05 14:51 by jkonczak
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