{"id":26,"date":"2022-03-04T15:11:13","date_gmt":"2022-03-04T20:11:13","guid":{"rendered":"https:\/\/pressbooks.library.ryerson.ca\/opsyshiraki\/chapter\/common-unix-commands\/"},"modified":"2025-09-07T08:57:56","modified_gmt":"2025-09-07T12:57:56","slug":"common-unix-commands","status":"publish","type":"chapter","link":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/chapter\/common-unix-commands\/","title":{"raw":"Common Unix Commands","rendered":"Common Unix Commands"},"content":{"raw":"

While there are hundreds of Unix commands, fortunately it is not necessary to know all of them. In fact, one can achieve a significant level of productivity knowing just a couple of dozen. Here are some of the most common and useful commands.<\/span><\/p>\r\n

All commands are case sensitive.<\/span><\/p>\r\n\r\n

\r\n

Spaces are a BIG DEAL in Unix<\/h2>\r\n

When issuing commands, in order for Unix to tell when a command finishes and when parameters and file names start and end, every item (or token) on a command line must be separated by whitespace (one or more space characters). One of the most common causes of frustration is failure to put whitepace between items on the command line, or putting whitespace where it should not be.<\/span><\/p>\r\n

Just as in English, there is a big difference in meaning between \"no table\" and \"notable\", or \"a trophy\" and \"atrophy\", so is the case in Unix.<\/span><\/p>\r\n

Right: <\/span><\/p>\r\n\r\n

ls \/etc<\/span><\/pre>\r\n
Wrong: <\/span><\/p>\r\n\r\n
ls\/etc<\/span><\/pre>\r\n<\/div>\r\n \r\n\r\nUnix commands are a single word requesting an action. Sometimes the action is standalone, but most actions are applied to some object like a file or directory. At the point in the command where it expects the name of a file, say, this is where you specify the file in the form of an absolute or relative reference as described in the previous chapter.\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Command<\/th>\r\nWhat does it do?<\/th>\r\nExample usage<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
ls<\/code><\/th>\r\nlist directory contents<\/td>\r\nList files (and directories) in my current directory:\r\nls<\/code>List files in top level etc directory:\r\nls \/etc<\/code>List all files beginning with g (wildcard *):\r\nls g*<\/code>\r\n\r\nList and give details about files:\r\nls -l<\/code>\r\n\r\nList all files including hidden:\r\nls -a<\/code><\/td>\r\n<\/tr>\r\n
cat<\/code><\/th>\r\nconcatenate files and print on the standard output<\/td>\r\nShow contents of file report:\r\ncat report<\/code>Show contents of files chapter1 and chapter2:\r\ncat chapter1 chapter2<\/code><\/td>\r\n<\/tr>\r\n
head<\/code><\/th>\r\noutput the first part of files<\/td>\r\nShow the first few lines of file longfile:\r\nhead longfile<\/code><\/td>\r\n<\/tr>\r\n
tail<\/code><\/th>\r\noutput the last part of files<\/td>\r\nShow the last few lines of file logfile:\r\ntail logfile<\/code><\/td>\r\n<\/tr>\r\n
cp<\/code><\/th>\r\ncopy files and directories<\/td>\r\nCopy file report to report_v2 in the work directory:\r\ncp report work\/report_v2<\/code><\/td>\r\n<\/tr>\r\n
mv<\/code><\/th>\r\nmove (rename) files<\/td>\r\nRename file report to presentation:\r\nmv report presentation<\/code>Move file mydata to yourdata one level up:\r\nmv mydata ..\/yourdata<\/code><\/td>\r\n<\/tr>\r\n
rm<\/code><\/th>\r\nremove files (permanent)<\/td>\r\nDelete file report in current directory:\r\nrm report<\/code>Caution:<\/strong> There is no recycling bin in Unix. Consider all deletions as permanent. Exercise care when using wildcards (e.g. *).<\/td>\r\n<\/tr>\r\n
cd<\/code><\/th>\r\nchange the working directory<\/td>\r\nChange directory to work directory (one level down):\r\ncd work<\/code>Change directory to \/bin directory:\r\ncd \/bin<\/code>Change directory to parent (one level up):\r\ncd ..<\/code>\r\n\r\nChange directory to home directory of user ahmed:\r\ncd ~ahmed<\/code><\/td>\r\n<\/tr>\r\n
pwd<\/code><\/th>\r\nprint name of current\/working directory<\/td>\r\nAre you lost?\r\npwd<\/code><\/td>\r\n<\/tr>\r\n
mkdir<\/code><\/th>\r\nmake directories<\/td>\r\nCreate new directory called unix_exercises:\r\nmkdir unix_exercises<\/code><\/td>\r\n<\/tr>\r\n
rmdir<\/code><\/th>\r\nremove empty directories<\/td>\r\nRemove (permanently delete) the directory unix_exercises:\r\nrmdir unix_exercises<\/code><\/td>\r\n<\/tr>\r\n
who<\/code><\/th>\r\nshow who is logged on<\/td>\r\nDisplay who else is logged in right now:\r\nwho<\/code><\/td>\r\n<\/tr>\r\n
whoami<\/code><\/th>\r\nprint effective userid<\/td>\r\nDisplay one's own userid (short login name):\r\nwhoami<\/code><\/td>\r\n<\/tr>\r\n
date<\/code><\/th>\r\nprint the system date and time<\/td>\r\ndate<\/code><\/td>\r\n<\/tr>\r\n
man<\/code><\/th>\r\nan interface to the on-line reference manuals<\/td>\r\nDisplay manual entry for ls command:\r\nman ls<\/code>Keyword search for commands related to \"directory\":\r\nman -k directory<\/code><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n \r\n
\r\n
Key Takeaways<\/p>\r\n\r\n<\/header>\r\n
\r\n
    \r\n \t
  • Spaces are a BIG DEAL in Unix: They are needed between commands, parameters, and filenames.<\/li>\r\n \t
  • All commands are case-sensitive (usually all lowercase)<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
    \r\n
    More Key Takeaways<\/p>\r\n\r\n<\/header>\r\n
    \r\n
      \r\n \t
    • Command options (e.g. -l, or -d, etc.) are specific to the command. For example, while both the ls and and cp command both have a \"-l\" option, the option means different things in each command. Command options are not<\/strong> mix and match.<\/li>\r\n \t
    • Command options may be listed separately or combined. The following are equivalent:\r\n
        \r\n \t
      • \r\n
        ls -ld<\/pre>\r\n<\/li>\r\n \t
      • \r\n
        ls -l -d<\/pre>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
        More Unix Commands<\/h2>\r\n
        All the commands below require some sort of input, typically a file, but the commands do not<\/strong> modify the input file. The outputs will contain portions of the input files, but the input files are never changed.<\/div>\r\n \r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
        Command<\/th>\r\nWhat does it do?<\/th>\r\nExample usage<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
        \r\n
        cut<\/pre>\r\n<\/th>\r\n
        		Print selected parts of lines from each FILE to standard output.<\/td>\r\ndisplay columns 1-10 and 20-23 of myfile\r\n
        cut -c1-10,20-23 myfile<\/pre>\r\ndisplay the 3rd and 5th fields of the \/etc\/passwd file\r\n
        cut -f3,5 -d: \/etc\/passwd<\/pre>\r\n <\/td>\r\n<\/tr>\r\n
        \r\n
        paste<\/pre>\r\n<\/th>\r\n
        		merge lines of files\r\n\r\nIf cat joins vertically, think of paste as a horizontal version of cat.<\/td>\r\ndisplay file1, file2, and file3 side-by-side\r\n
        paste file1 file2 file3<\/pre>\r\n <\/td>\r\n<\/tr>\r\n
        \r\n
        wc<\/pre>\r\n<\/th>\r\n
        		print newline, word, and byte counts for each file<\/td>\r\ndisplay the number of lines, words, and characters for the file chapter3\r\n
        wc chapter3<\/pre>\r\ndisplay only the number of lines\r\n
        wc -l chapter3<\/pre>\r\n <\/td>\r\n<\/tr>\r\n
        \r\n
        grep<\/pre>\r\n<\/th>\r\n
        		print lines matching a pattern<\/td>\r\ndisplay lines matching the string Total in the file sales\r\n
        grep Total sales<\/pre>\r\n <\/td>\r\n<\/tr>\r\n
        \r\n
        sort<\/pre>\r\n<\/th>\r\n
        		sort lines of text files<\/td>\r\ndisplay a sorted version of the file namelist\r\n
        sort namelist<\/pre>\r\n <\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n \r\n\r\n ","rendered":"
        While there are hundreds of Unix commands, fortunately it is not necessary to know all of them. In fact, one can achieve a significant level of productivity knowing just a couple of dozen. Here are some of the most common and useful commands.<\/span><\/p>\n
        All commands are case sensitive.<\/span><\/p>\n
        \n
        Spaces are a BIG DEAL in Unix<\/h2>\n
        When issuing commands, in order for Unix to tell when a command finishes and when parameters and file names start and end, every item (or token) on a command line must be separated by whitespace (one or more space characters). One of the most common causes of frustration is failure to put whitepace between items on the command line, or putting whitespace where it should not be.<\/span><\/p>\n
        Just as in English, there is a big difference in meaning between “no table” and “notable”, or “a trophy” and “atrophy”, so is the case in Unix.<\/span><\/p>\n
        Right: <\/span><\/p>\n
        ls \/etc<\/span><\/pre>\n
        Wrong: <\/span><\/p>\n
        ls\/etc<\/span><\/pre>\n<\/div>\n
         <\/p>\n
        Unix commands are a single word requesting an action. Sometimes the action is standalone, but most actions are applied to some object like a file or directory. At the point in the command where it expects the name of a file, say, this is where you specify the file in the form of an absolute or relative reference as described in the previous chapter.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
        Command<\/th>\nWhat does it do?<\/th>\nExample usage<\/th>\n<\/tr>\n<\/thead>\n
        ls<\/code><\/th>\nlist directory contents<\/td>\nList files (and directories) in my current directory:
        \nls<\/code>List files in top level etc directory:
        \nls \/etc<\/code>List all files beginning with g (wildcard *):
        \nls g*<\/code><\/p>\n
        List and give details about files:
        \nls -l<\/code><\/p>\n
        List all files including hidden:
        \nls -a<\/code><\/td>\n<\/tr>\n
        cat<\/code><\/th>\nconcatenate files and print on the standard output<\/td>\nShow contents of file report:
        \ncat report<\/code>Show contents of files chapter1 and chapter2:
        \ncat chapter1 chapter2<\/code><\/td>\n<\/tr>\n
        head<\/code><\/th>\noutput the first part of files<\/td>\nShow the first few lines of file longfile:
        \nhead longfile<\/code><\/td>\n<\/tr>\n
        tail<\/code><\/th>\noutput the last part of files<\/td>\nShow the last few lines of file logfile:
        \ntail logfile<\/code><\/td>\n<\/tr>\n
        cp<\/code><\/th>\ncopy files and directories<\/td>\nCopy file report to report_v2 in the work directory:
        \ncp report work\/report_v2<\/code><\/td>\n<\/tr>\n
        mv<\/code><\/th>\nmove (rename) files<\/td>\nRename file report to presentation:
        \nmv report presentation<\/code>Move file mydata to yourdata one level up:
        \nmv mydata ..\/yourdata<\/code><\/td>\n<\/tr>\n
        rm<\/code><\/th>\nremove files (permanent)<\/td>\nDelete file report in current directory:
        \nrm report<\/code>Caution:<\/strong> There is no recycling bin in Unix. Consider all deletions as permanent. Exercise care when using wildcards (e.g. *).<\/td>\n<\/tr>\n
        cd<\/code><\/th>\nchange the working directory<\/td>\nChange directory to work directory (one level down):
        \ncd work<\/code>Change directory to \/bin directory:
        \ncd \/bin<\/code>Change directory to parent (one level up):
        \ncd ..<\/code><\/p>\n
        Change directory to home directory of user ahmed:
        \ncd ~ahmed<\/code><\/td>\n<\/tr>\n
        pwd<\/code><\/th>\nprint name of current\/working directory<\/td>\nAre you lost?
        \npwd<\/code><\/td>\n<\/tr>\n
        mkdir<\/code><\/th>\nmake directories<\/td>\nCreate new directory called unix_exercises:
        \nmkdir unix_exercises<\/code><\/td>\n<\/tr>\n
        rmdir<\/code><\/th>\nremove empty directories<\/td>\nRemove (permanently delete) the directory unix_exercises:
        \nrmdir unix_exercises<\/code><\/td>\n<\/tr>\n
        who<\/code><\/th>\nshow who is logged on<\/td>\nDisplay who else is logged in right now:
        \nwho<\/code><\/td>\n<\/tr>\n
        whoami<\/code><\/th>\nprint effective userid<\/td>\nDisplay one’s own userid (short login name):
        \nwhoami<\/code><\/td>\n<\/tr>\n
        date<\/code><\/th>\nprint the system date and time<\/td>\ndate<\/code><\/td>\n<\/tr>\n
        man<\/code><\/th>\nan interface to the on-line reference manuals<\/td>\nDisplay manual entry for ls command:
        \nman ls<\/code>Keyword search for commands related to “directory”:
        \nman -k directory<\/code><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
         <\/p>\n
        \n
        \n
        Key Takeaways<\/p>\n<\/header>\n
        \n
          \n
        • Spaces are a BIG DEAL in Unix: They are needed between commands, parameters, and filenames.<\/li>\n
        • All commands are case-sensitive (usually all lowercase)<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
          \n
          \n
          More Key Takeaways<\/p>\n<\/header>\n
          \n
            \n
          • Command options (e.g. -l, or -d, etc.) are specific to the command. For example, while both the ls and and cp command both have a “-l” option, the option means different things in each command. Command options are not<\/strong> mix and match.<\/li>\n
          • Command options may be listed separately or combined. The following are equivalent:\n
              \n
            • \n
              ls -ld<\/pre>\n<\/li>\n
            • \n
              ls -l -d<\/pre>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
               <\/p>\n<\/div>\n<\/div>\n
              More Unix Commands<\/h2>\n
              All the commands below require some sort of input, typically a file, but the commands do not<\/strong> modify the input file. The outputs will contain portions of the input files, but the input files are never changed.<\/div>\n
               <\/p>\n\n\n\n\n\n\n\n\n\n
              Command<\/th>\nWhat does it do?<\/th>\nExample usage<\/th>\n<\/tr>\n<\/thead>\n
              \n
              cut<\/pre>\n<\/th>\n
              		Print selected parts of lines from each FILE to standard output.<\/td>\ndisplay columns 1-10 and 20-23 of myfile<\/p>\n
              cut -c1-10,20-23 myfile<\/pre>\n
              display the 3rd and 5th fields of the \/etc\/passwd file<\/p>\n
              cut -f3,5 -d: \/etc\/passwd<\/pre>\n
               <\/td>\n<\/tr>\n
              \n
              paste<\/pre>\n<\/th>\n
              		merge lines of files<\/p>\n
              If cat joins vertically, think of paste as a horizontal version of cat.<\/td>\n
              		display file1, file2, and file3 side-by-side<\/p>\n
              paste file1 file2 file3<\/pre>\n
               <\/td>\n<\/tr>\n
              \n
              wc<\/pre>\n<\/th>\n
              		print newline, word, and byte counts for each file<\/td>\ndisplay the number of lines, words, and characters for the file chapter3<\/p>\n
              wc chapter3<\/pre>\n
              display only the number of lines<\/p>\n
              wc -l chapter3<\/pre>\n
               <\/td>\n<\/tr>\n
              \n
              grep<\/pre>\n<\/th>\n
              		print lines matching a pattern<\/td>\ndisplay lines matching the string Total in the file sales<\/p>\n
              grep Total sales<\/pre>\n
               <\/td>\n<\/tr>\n
              \n
              sort<\/pre>\n<\/th>\n
              		sort lines of text files<\/td>\ndisplay a sorted version of the file namelist<\/p>\n
              sort namelist<\/pre>\n
               <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
               <\/p>\n
               <\/p>\n","protected":false},"author":2,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-26","chapter","type-chapter","status-publish","hentry"],"part":23,"_links":{"self":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/chapters\/26","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/wp\/v2\/users\/2"}],"version-history":[{"count":12,"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/chapters\/26\/revisions"}],"predecessor-version":[{"id":124,"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/chapters\/26\/revisions\/124"}],"part":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/parts\/23"}],"metadata":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/chapters\/26\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/wp\/v2\/media?parent=26"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/pressbooks\/v2\/chapter-type?post=26"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/wp\/v2\/contributor?post=26"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.library.torontomu.ca\/opsyshiraki\/wp-json\/wp\/v2\/license?post=26"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}