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Question with read command in ksh
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shell_builtins(1) User Commands shell_builtins(1) NAME
shell_builtins, case, for, foreach, function, if, repeat, select, switch, until, while - shell command interpreter built-in commands DESCRIPTION
The shell command interpreters csh(1), ksh(1), ksh93(1), and sh(1) have special built-in commands. The commands case, for, foreach, func- tion, if, repeat, select, switch, until, and while are commands in the syntax recognized by the shells. They are described in the Commands section of the manual pages of the respective shells. In ksh93(1), fc, hash, stop, suspend, times, and type are aliases by default. In ksh93, the following built-ins are bound to the /bin pathname by default and are invoked if the pathname search encounters an executable command of that name in the /bin or /usr/bin directory: cat, chown, getconf, head, mkdir, rmdir, tee, uniq, and wc. The remaining commands listed in the following table are built into the shells for reasons such as efficiency or data sharing between com- mand invocations. They are described on their respective manual pages. Command Shell ----------------------------------------------------------- ++**alias csh, ksh, ksh93 bg csh, ksh, ksh93, sh +*break csh, ksh, ksh93, sh builtin ksh93 case csh, ksh, ksh93, sh cat ksh93 cd csh, ksh, ksh93, sh chdir csh, sh chown ksh93 command ksh93 +*continue csh, ksh, ksh93, sh dirs csh disown ksh93 echo csh, ksh, ksh93, sh +*eval csh, ksh, ksh93, sh +*exec csh, ksh, ksh93, sh +*exit csh, ksh, ksh93, sh ++**export ksh, ksh93, sh false ksh, ksh93 fc ksh, ksh93 fg csh, ksh, ksh93, sh for ksh, ksh93, sh foreach csh function ksh, ksh93 getconf ksh93 getopts ksh, ksh93, sh glob csh goto csh hash ksh, ksh93, sh hashstat csh head ksh93 hist ksh93 history csh if csh, ksh, ksh93, sh jobs csh, ksh, ksh93, sh kill csh, ksh, ksh93, sh let ksh, ksh93, limit csh login csh, ksh, ksh93, sh logout csh mkdir ksh93 nice csh +*newgrp ksh, ksh93, sh nohup csh notify csh onintr csh popd csh print ksh, ksh93 printf ksh93 pushd csh pwd ksh, ksh93, sh read ksh, ksh93, sh ++**readonly ksh, ksh93, sh rehash csh repeat csh +*return ksh, ksh93, sh select ksh, ksh93 +set csh, ksh, ksh93, sh setenv csh shift csh, ksh, ksh93, sh sleep ksh93 source csh stop csh, ksh, ksh93, sh suspend csh, ksh, sh switch csh tee ksh93 test ksh, ksh93, sh time csh *times ksh, ksh93, sh *+trap ksh, ksh93, sh true ksh, ksh93 type ksh, ksh93, sh ++**typeset ksh, ksh93 ulimit ksh, ksh93, sh umask csh, ksh, ksh93, sh +unalias csh, ksh, ksh93 unhash csh uniq ksh93 unlimit csh +unset csh, ksh, ksh93, sh unsetenv csh until ksh, ksh93, sh *wait csh, ksh, ksh93, sh whence ksh, ksh93 while csh, ksh, ksh93, sh Bourne Shell, sh, Special Commands Input/output redirection is now permitted for these commands. File descriptor 1 is the default output location. When Job Control is enabled, additional Special Commands are added to the shell's environment. In addition to these built-in reserved command words, sh also uses: : No effect; the command does nothing. A zero exit code is returned. .filename Read and execute commands from filename and return. The search path specified by PATH is used to find the directory contain- ing filename. C shell, csh Built-in commands are executed within the C shell. If a built-in command occurs as any component of a pipeline except the last, it is exe- cuted in a subshell. In addition to these built-in reserved command words, csh also uses: : Null command. This command is interpreted, but performs no action. Korn Shell, ksh, Special Commands Input/Output redirection is permitted. Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when there is no syntax error, is zero. Commands that are preceded by one or two * (asterisks) are treated specially in the following ways: 1. Variable assignment lists preceding the command remain in effect when the command completes. 2. I/O redirections are processed after variable assignments. 3. Errors cause a script that contains them to abort. 4. Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file name genera- tion are not performed. In addition to these built-in reserved command words, ksh also uses: * : [ arg ... ] The command only expands parameters. * .file [ arg ... ] Read the complete file then execute the commands. The commands are executed in the current shell environment. The search path specified by PATH is used to find the directory containing file. If any arguments arg are specified, they become the positional parameters. Otherwise, the positional parameters are unchanged. The exit status is the exit status of the last command executed. the loop termination test. Korn Shell, ksh93, Special Commands Input/Output redirection is permitted. Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when there is no syntax error, is zero. Except for :, true, false, echo, newgrp, and login, all built-in commands accept -- to indicate end of options. They also interpret the option --man as a request to display the manual page onto standard error and -? as a help request which prints a usage message on standard error. Commands that are preceded by one or two + are treated specially in the following ways: 1. Variable assignment lists preceding the command remain in effect when the command completes. 2. I/O redirections are processed after variable assignments. 3. Errors cause a script that contains them to abort. 4. They are not valid function names. 5. Words, following a command preceded by ++ that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the = sign and field splitting and file name genera- tion are not performed. In addition to these built-in reserved command words, ksh93 also uses: : [ arg ... ] The command only expands parameters. .name [ arg ... ] If name is a function defined with the function name reserved word syntax, the function is executed in the cur- rent environment (as if it had been defined with the name() syntax.) Otherwise if name refers to a file, the file is read in its entirety and the commands are executed in the current shell environment. The search path specified by PATH is used to find the directory containing the file. If any arguments arg are specified, they become the positional parameters while processing the . command and the original positional parameters are restored upon completion. Otherwise the positional parameters are unchanged. The exit status is the exit status of the last command executed. SEE ALSO
Intro(1), alias(1), break(1), builtin(1), cd(1), chmod(1), csh(1), disown(1), echo(1), exec(1), exit(1), find(1), getoptcvt(1), getopts(1), glob(1), hash(1), history(1), jobs(1), kill(1), ksh(1), ksh93(1), let(1), limit(1), login(1), logout(1), newgrp(1), nice(1), nohup(1), print(1), printf(1), pwd(1), read(1), readonly(1), set(1), sh(1), shift(1), sleep(1), suspend(1), test(1)test(1), test(1B), time(1), times(1), trap(1), typeset(1), umask(1), wait(1), chdir(2), chmod(2), creat(2), umask(2), getopt(3C), profile(4), environ(5) SunOS 5.11 20 Nov 2007 shell_builtins(1)
